Specific Concentration Range Research Articles

Acute toxicity and gene responses induced by endosulfan in zebrafish (Danio rerio) embryos

Endosulfan has been listed as a persistent organic pollutant, and is frequently found in agricultural environments during monitoring processes owing to its heavy use and persistent characteristics. This study was conducted to understand the effects of endosulfan on the development of zebrafish (Danio rerio) embryos by exposing them to a specific range of endosulfan concentrations. Exposing zebrafish embryos to endosulfan for 96 h yielded no acute toxicity until the concentration reached 1500 μg L−1, whereas malformed zebrafish larvae developed severely curved spines and shortened tails. About 50% of zebrafish larvae were malformed when exposed to 600 μg L−1 of endosulfan. Comparative gene expression using real-time quantitative polymerase chain reaction was assessed using endosulfan-exposed zebrafish embryos. CYP1A and CYP3A were significantly enhanced in response to endosulfan treatment. Two genes, acacb and fasn, encoding acetyl-CoA carboxylase b and fatty acid synthase proteins, respectively, were also up-regulated after treating zebrafish embryos with endosulfan. These genes are also involved in fatty acid biosynthesis. The genes encoding vitellogenin and Hsp70 increased in a concentration-dependent manner in embryos. Finally, biochemical studies showed that acetylcholinesterase activity was reduced, whereas glutathione S-transferase and carboxylesterase activities were enhanced in zebrafish embryos after endosulfan treatment. These biochemical and molecular biological differences might be used for tools to determine contamination of endosulfan in the aquatic environment.

Insights into sliding wear and friction behavior of copper in ethanol containing alkylphosphonic acid molecules

In this work, the friction and wear behavior of bare copper was investigated for the first time under lubricated sliding conditions in diluted ethanol solutions of butylhosphonic (C4P), octylphosphonic (C8P), dodecylphosphonic (C12P), and hexadecylphosphonic (C16P) acids. The technique aims towards a more environmentally friendly lubrication to be used in shaping of copper sheets. Bare copper samples were subjected to unidirectional sliding using a tribometer with ball-on-disk contact geometry. Copper substrates (20mm2×1mm) were run against 100Cr6 Ø10mm ball bearing counterbodies. All tests were conducted using the same sliding conditions with a normal load of 10N, tangential velocity of 0.01m/s, at room temperature of 20°C. Worn surfaces were analyzed by Scanning Electron Microscopy, Optical Microscopy and White Light Interference Profilometry. When comparing to sliding tests in the pure ethanol solvent, significant decreases in terms of wear track dimensions, transferred material on the ball and friction coefficients are observed when active molecules are present in the solution. These form protective tribofilms exhibiting lubricating and anti-wear properties.Deeper studies on the tribological behavior of copper in C4P solution show that both low friction and low transfer of work material to the ball prevail in a specific range of low molecule concentration (5×10−4M; 25×10−4M). Even if the molecules are introduced during the test, after a few cycles, the tribological behavior improves, regardless of both friction level and copper surface degradation. Finally, specific friction tests were performed to further investigate the mechanisms. It was found that two mechanisms are involved; firstly molecules grafting onto the surface directly reduces friction, and secondly transformation of these grafted molecules into a tribofilm during the first mechanical contact cycles reduces it even further.

Light‐Induced Reversible Self‐Assembly of Gold Nanoparticles Surface‐Immobilized with Coumarin Ligands

AbstractA novel light‐induced reversible self‐assembly (LIRSA) system is based on the reversible photodimerization and photocleavage of coumarin groups on the surface of gold nanoparticles (AuNPs) in THF solution. Facilitated by coumarin groups, light irradiation at 365 nm triggers the stable assembly of monodisperse AuNPs; the resulting self‐assembly system can be disassembled back to the disassembled state by a relatively short exposure to benign UV light. The reversible self‐assembly cycle can be repeated 4 times. A specific concentration range of coumarin ligand and the THF solvent were identified to be the two predominant factors that contribute to the LIRSA of AuNPs. This is the first successful application of reversible photodimerization based on a coumarin derivative in the field of AuNP LIRSA. This LIRSA system may provide unique opportunities for the photoregulated synthesis of many adjustable nanostructures and devices.

Light-Induced Reversible Self-Assembly of Gold Nanoparticles Surface-Immobilized with Coumarin Ligands.

A novel light-induced reversible self-assembly (LIRSA) system is based on the reversible photodimerization and photocleavage of coumarin groups on the surface of gold nanoparticles (AuNPs) in THF solution. Facilitated by coumarin groups, light irradiation at 365 nm triggers the stable assembly of monodisperse AuNPs; the resulting self-assembly system can be disassembled back to the disassembled state by a relatively short exposure to benign UV light. The reversible self-assembly cycle can be repeated 4 times. A specific concentration range of coumarin ligand and the THF solvent were identified to be the two predominant factors that contribute to the LIRSA of AuNPs. This is the first successful application of reversible photodimerization based on a coumarin derivative in the field of AuNP LIRSA. This LIRSA system may provide unique opportunities for the photoregulated synthesis of many adjustable nanostructures and devices.

Bioaccumulation and tolerance characteristics of a submerged plant (Ceratophyllum demersum L.) exposed to toxic metal lead

A hydroponic study was conducted to investigate the lead bioaccumulation and tolerance characteristics of Ceratophyllum demersum L. exposed to various lead concentrations (5–80μM) for 7, 14 or 21 days. Lead accumulation increased with increasing concentrations of metal in the solution, to a maximum accumulation of 4016.4mgkg–1 dw. Unexpectedly, the release of accumulated lead from the plants into solution was observed for all experimental groups except those exposed to 5μM. Both the biomass and protein content of the plants responded significantly to lead stress. Malondialdehyde (MDA) levels increased substantially at lead concentrations below 20μM, further indicating that this metal is toxic to the plants. To reveal the mechanism underlying the defense against lead stress, plants were also assayed for the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), as well as other relevant enzymes such as phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO). The activities of both SOD and CAT increased at lower lead concentrations and with shorter exposure times, followed by a decline, but the activities of POD and its isoenzymes continued to increase under all conditions. Moreover, increases in the activities of PAL and PPO were observed only for the 14-day treatment, and these two enzymes were not sensitive to lead concentration. These results suggest that C. demersum exhibits strong tolerance within a specific concentration range of lead in solution; according to regression analysis, 40μM is suggested to be this plant's tolerance threshold for lead in water. Furthermore, the malfunction of this tolerance mechanism might accelerate the metal-release process. These attributes are likely to be beneficial for utilizing C. demersum in phytoremediation applications.

Validation of WRF/Chem model and sensitivity of chemical mechanisms to ozone simulation over megacity Delhi

Abstract Regional Chemical transport models (CTM) are used extensively for modeling of Ozone concentration. WRF/Chem is one such CTM that includes various chemical mechanisms and is used for simulation of Ozone and other pollutant concentration at desired time step. This study focuses on the robustness of WRF/Chem simulated Ozone concentrations over a sub tropical urban airshed of megacity Delhi. Detailed analysis has been presented for the veracity of two different chemical mechanisms namely; Carbon Bond Mechanism (CBMZ) and Regional Atmospheric Chemical Model (RACM). It was observed that simulated Ozone concentrations are better predicted with CBMZ mechanism and is highly sensitive to the rate constants. The Ozone concentrations are analyzed for precursors such as Oxides of Nitrogen (NOx) and Carbon-monoxide (CO) as well as temperature considering their strong dependence on Ozone formation. A consistent positive correlation between Ozone concentration and temperature is noted whereas; NOx and CO show inverse relationship with Ozone. Further, Ozone concentration range vis-a-vis model performance is scrutinized. A poor model for low Ozone concentration levels is observed and a highly satisfactory for moderate Ozone concentration levels while satisfactory for higher Ozone levels. Despite of the limitations observed during model evaluation of Ozone predictions for low Ozone levels, it is concluded that WRF/Chem could effectively be applied for understanding its trends, tropospheric chemistry and air quality assessment for regulatory purposes at moderate Ozone concentration levels. Further, it is recommended that model implementation shall be made for policy decisions cautiously with due consideration to the magnitudes of Ozone levels present in the study domain and the performance measures in the specific concentration range.

Assessment of genetic toxicity with major inhalable mineral granules in A549 cells

The toxicity of inhalable mineral granules has become a great interest topic of air pollution in the international. The majority of research in this area has focused on organic components that adhere to inhalable granules and on the pathogenicity of granules-associated heavy metal ions. However, as the main components of the mineral grains of dust, inhalable mineral granules is an important part of the dust, the granules themselves also represent important pathogenic factors. Whether the inhalable mineral granule in China has the genetic toxicity is unknown. To determine whether the mineral granules are genotoxic, a specific concentration range for 6 major components of the inhalable minerals in China were selected. The human lung adenocarcinoma cell line A549 was used to study granules genetic toxicity. Wright–Giemsa staining was used to evaluate cell morphology, the methyl thiazolyl tetrazolium (MTT) assay was used to determine any effects on cell proliferation, micronucleus tests were conducted to observe the effects of the minerals on the formation of chromosomal breaks and sister chromosome exchange (SCE) experiments were used to assess whether DNA synthesis was affected. The experimental results indicated the following: The membrane destruction, nuclear pyknosis, and mineral surface adhesion were observed in A549 cells treated with sericite or albite. In cells treated with quartz or montmorillonite, gaps between the cells were increased in size, the cells appeared more loosely arranged and became smaller than those of the control group, and a large amount of granules adsorbed to the cell surface. The inhibitory effect of the minerals tested on the proliferation of A549 cells ranked as follows, from most to least inhibitory: nano-montmorillonite, nano-SiO2, nano-sericite, nano-quartz, albite, and nano-calcite. Mineral granules concentration correlated with an inhibition of the cell proliferation rate. As the concentration of the mineral granules increased, the incidence of micronuclei gradually increased for all minerals. All mineral granules tested caused DNA damage in the cells in a dose-dependent manner, as higher concentrations of mineral granules caused more DNA damage. These results indicate that inhalable mineral granules may be genotoxic to cells.

Optical path length and absorption cross section optimization for high sensitivity ozone concentration measurement

Long optical path length and strong ozone absorption wavelength are generally applied for high sensitivity ozone concentration measurement in ultraviolet absorption spectroscopy. However, high sensitivity of measurement cannot be achieved when the sensor approaches saturation. Here, we derive two equations based on Beer–Lambert law to optimize the sensitivity of measurement. Firstly, we optimize the optical path length for high sensitivity measurement of specific range of ozone concentration. Secondly, we optimize the absorption cross section for proper selection of ozone sampling wavelength to prevent sensor saturation. Simulation and experimental results show high sensor sensitivity for a gas cell of optimized optical path length. High sensitivity of measurement is achieved when the sensor is not saturated. We have validated the requirements for high sensitivity ozone concentration measurement through theoretical calculation, spectralcalc.com simulation and experiment.

Semi-adaptive response and noise attenuation in bone morphogenetic protein signalling.

Temporal dynamics of morphogen-driven signalling events are critical for proper embryonic development. During development, cells translate extracellular bone morphogenetic protein (BMP) gradients, often subject to noise, into graded intracellular tail-phosphorylated SMAD (TP-SMAD) levels. Using modelling and experimental approaches, we found that BMPs induce TP-SMAD responses in neural precursor cells in a concentration-dependent manner, which are semi-adaptive within a specific intermediate range of BMP concentration. These semi-adaptive TP-SMAD responses involve an intrinsically slow deactivation of BMP receptors, which attenuates noise by prolonging SMAD deactivation time after BMP withdrawal, but increases response time. Interestingly, negative feedback on BMP receptors is also required for semi-adaptation, which benefits both noise attenuation and response time, and therefore balances the trade-off seen with slow BMP receptor deactivation. These results highlight the rich dynamics of SMAD regulation in response to graded BMP concentration, and elucidate general design principles for balancing noise attenuation and activation speed in signalling systems.

Stabilization of self‐assembled microdroplets using short chain alcohols

ABSTRACTThe condensation of water vapor on a volatile polymeric solution leads to a porous surface after evaporation of both solvent and water. However, the stabilization of the water microdroplet is of great importance, which can be achieved using specific polymer or adding a third substance to the polymer solution. Short chain alcohols (methanol, ethanol, and n‐propanol) are utilized to fabricate a self‐assembled porous honeycomb film of linear, low molecular weight polystyrene using the breath figure technique. A combination of breath figure processing and the effect of alcohol on a water droplet can stabilize the pattern and make pores on the surface of the polymer film. The quality of the porous honeycomb film is strongly dependent on the type of alcohols and the concentration of polymer. In a specific range of polymer and alcohol concentration, pores cover all the surface of the polymer film. This method offers the possibility of producing a honeycomb structure with no trace of additive residual after the fabrication process and avoiding polymer modification. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 709–718

Micelle-Vesicle Transition by Cleavage of Disulfide Spacer Chain for Gemini Surfactant in Didodecyldimethylammonium Chloride Aqueous Solutions.

We examined the "micelle-vesicle transition" through the mixing effect of single-tailed thiol surfactants produced by the cleavage of gemini surfactants, [C12H25N(CH3)2CH2CH2SSCH2CH2N(CH3)2C12H25] 2Cl (C12SSC12), which have a disulfide bond in the spacer chain. Phase diagrams of C12H25N(CH3)2CH2CH2SHCl-didodecyldimethylammonium chloride (C12SH-DDAC) and C12SSC12-DDAC were determined by conductivity and pyrene fluorescence probe methods. The aggregate diameters were evaluated by dynamic light scattering (DLS). The critical vesicle concentration (CVC) was confirmed by the abrupt increase in the intensity of light scattering with excitation at 335 nm. Vesicle formation was confined to the DDAC-rich region of the C12SSC12-DDAC system, while the vesicle formation region for the C12SH-DDAC system spread out with the addition of dithiothreitol (DTT) to C12SSC12-DDAC. This implies that single-tailed surfactants can induce a more favorable environment for molecular packing of the vesicular surface. The micelle-vesicle transition occurs with disulfide spacer chain cleavage of gemini surfactants at a particular specific concentration range.

Influence of emulsifier concentration on nanoemulsion gelation.

Nanoemulsion gels are a new class of soft materials that manifest stronger elasticity even at lower dispersed phase volume fraction. In this work, gelation in 40 wt % canola oil-in-water nanoemulsions was investigated as a function of emulsifier type (anionic sodium dodecyl sulfate (SDS) or nonionic Tween 20) and concentration. It was observed that the liquid nanoemulsions transformed into viscoelastic gels at a specific concentration range of SDS, whereas no gelation was observed for Tween 20. The apparent viscosity, yield stress, and storage modulus of the nanogels increased with SDS concentration until 15 times critical micelle concentration (CMC), thereafter decreased steadily as the gelation weakened beginning 20 CMC. Three regimes of colloidal interactions in the presence of emulsifier were proposed. (1) Repulsive gelation: at low SDS concentration (0.5-2 times CMC) the repulsive charge cloud around the nanodroplets acted as interfacial shell layer that significantly increased the effective volume fraction of the dispersed phase (ϕ(eff)). When ϕ(eff) became comparable to the volume fraction required for maximal random jamming, nanoemulsions formed elastic gels. (2) Attractive gelation: as the SDS concentration increased to 5-15 times CMC, ϕ(eff) dropped due to charge screening by more counterions from SDS, but depletion attractions generated by micelles in the continuous phase led to extensive droplet aggregation which immobilized the continuous phase leading to stronger gel formation. (3) Decline in gelation due to oscillatory structural forces (OSF): at very high SDS concentration (20-30 time CMC), structural forces were manifested due to the layered-structuring of excess micelles in the interdroplet regions resulting in loss of droplet aggregation. Tween 20 nanoemulsions, on the other hand, did not show repulsive gelation due to lack of charge cloud, while weak depletion attraction and early commencement of OSF regime leading to liquid-like behavior at all concentrations. The nanogels possess great potential for use in low-fat foods, pharmaceuticals and cosmetic products.

A Generic Method for Design of Oligomer-Specific Antibodies

Antibodies that preferentially and specifically target pathological oligomeric protein and peptide assemblies, as opposed to their monomeric and amyloid counterparts, provide therapeutic and diagnostic opportunities for protein misfolding diseases. Unfortunately, the molecular properties associated with oligomer-specific antibodies are not well understood, and this limits targeted design and development. We present here a generic method that enables the design and optimisation of oligomer-specific antibodies. The method takes a two-step approach where discrimination between oligomers and fibrils is first accomplished through identification of cryptic epitopes exclusively buried within the structure of the fibrillar form. The second step discriminates between monomers and oligomers based on differences in avidity. We show here that a simple divalent mode of interaction, as within e.g. the IgG isotype, can increase the binding strength of the antibody up to 1500 times compared to its monovalent counterpart. We expose how the ability to bind oligomers is affected by the monovalent affinity and the turnover rate of the binding and, importantly, also how oligomer specificity is only valid within a specific concentration range. We provide an example of the method by creating and characterising a spectrum of different monoclonal antibodies against both the Aβ peptide and α-synuclein that are associated with Alzheimer's and Parkinson's diseases, respectively. The approach is however generic, does not require identification of oligomer-specific architectures, and is, in essence, applicable to all polypeptides that form oligomeric and fibrillar assemblies.

Influences of H<sub>2</sub>SO<sub>4</sub> and NaCl Concentrations on Stress Corrosion Cracking of AISI 304 Stainless Steel

This paper presents the influence of H2SO4 and NaCl concentrations on the corrosion mode of AISI 304 stainless steel in H2SO4-NaCl aqueous solutions. Immersion test was conducted at room temperature using U-bend specimens. The specimens in annealed and sensitized conditions were immersed in aqueous solutions containing H2SO4 concentration in the range of 0 to 3.0 kmol/m3 with 1.5 kmol/m3 interval, and NaCl concentration in the range of 0.5 to 2.0 kmol/m3 with 0.5 kmol/m3 interval. Results showed that, specimens in sensitized condition have a higher mass loss and higher corrosion rate. In addition, the experimental result also indicates that the two solutes have synergistic effect on corrosion mode of the material that is stress corrosion cracking (SCC) and general corrosion, which occur within a specific range of concentration. SCC region became smaller as the H2SO4 and NaCl concentration increased. However, the occurrence of SCC was high when sensitization treatment was subjected to the specimens. The appearance of surface damage and crack morphology were revealed by using scanning electron microscopy (SEM).

Electrolyte Effect on Lamellar Domain Morphology in a Nonionic Surfactant Solution below the Krafft Temperature

In our previous papers, we have studied the lamellar domain morphology in aqueous solutions of nonionic surfactants C16E6 and C16E7 below the Krafft temperature. In this study, electrolyte effects on lamellar domain morphology have been investigated by means of DSC, confocal microscope, small/wide-angle X-ray scattering (SAXS/WAXS). It has been found that vesicles in C16E7 solution are transformed to network structures by adding chaotropic ion Cl(-), F(-) and CH3COO(-), whereas the network structures in C16E6 solution are gradually changed to the vesicles with increasing kosmotropic ion SCN(-) concentration. Especially, we focused on the SCN(-) ion effects on the C16E6 system, and found that the characteristic morphology of cylinder-like domains were formed in a certain specific concentration range. In the SAXS observation in nm scale, we have also found that the repeat distance of lamellar structures in the C16E6/NaSCN solution is anomalously swollen when adding 1.2-2 mol/kg NaSCN, where the cylinder-like domains are formed. We have concluded that the cylindrical vesicles could be explained by the osmotic pressure difference due to the addition of NaSCN.

Effect of puerarin on matrix metalloproteinase-2 in human fetal scleral fibroblasts treated with low frequency electromagnetic fields

ObjectiveTo study the effect of puerarin on matrix metalloproteinase-2 (MMP-2) gene and protein expression in human fetal scleral fibroblasts (HFSFs) exposed to extremely low frequency electromagnetic fields (ELF-EMF). MethodsCultured HFSFs were exposed to 0.2 mT ELF-EMF for 24 h. The experimental groups were divided into subgroups treated with 0, 0.1, 1 and 10 µM puerarin respectively. The expression of MMP-2 mRNA and protein were detected with real-time polymerase chain reaction and western-blot analysis respectively. ResultsMMP-2 mRNA and protein expression increased by 0.793 and 1.130 folds respectively under the exposure of ELF-EMFs at 0.2 mT flux density for 24 h. Puerarin at the concentration of 0.1 μM reversed this effect by 8.53% in mRNA and by 17.97% in protein expression (P<0.05). The effect was more prominent at higher concentrations (1 and 10 μM, P<0.01). ConclusionExposure to ELF-EMFs increased the expression of MMP-2 mRNA and protein in HFSF cells. Puerarin reversed the action to some extent in a specific concentration range. Our results implied that the puerarin might protect scleral tissue from increased expression induced by exposure to ELF-EMFs.

The Influence of the Cooling Rate on the Nucleation Efficiency of Isotactic Poly(propylene) with Bis(3,4‐dimethylbenzylidene)sorbitol

SummaryThe phase behavior of isotactic poly(propylene) (i‐PP) and 1,3:2,4‐bis(3,4‐dimethylbenzylidene)sorbitol (DMDBS) was studied by using differential scanning calorimetry (DSC), rheology and optical microscopy and can be characterized by a simple binary monotectic phase diagram. DMDBS is a well‐known nucleating and clarifying agent for i‐PP that forms a fibrillar network upon cooling from a homogeneous melt within a specific concentration range. The influence of the cooling rate and the residence time in regime II of the phase diagram on the formation of the fibrillar network and the ratio between the α‐ and mesophase is investigated. This shows that DMDBS is actually a better nucleation agent for i‐PP when it is given less time for gelation, since the formation of a ‘secondary’ structure, in which the thin elementary nano‐fibrils form bundles of thicker fibrils, results in a decrease of the surface area that is available for nucleation.

Effects of Exogenous Zinc on Cell Cycle, Apoptosis and Viability of MDAMB231, HepG2 and 293 T Cells

As a non-toxic metal to humans, zinc is essential for cell proliferation, differentiation, regulation of DNA synthesis, genomic stability and mitosis. Zinc homeostasis in cells, which is crucial for normal cellular functioning, is maintained by various protein families including ZnT (zinc transporter/SLC30A) and ZIP (Zrt-, Irt-like proteins/SLC39A) that decrease and increase cytosolic zinc availability, respectively. In this study, we investigated the influences of a specific concentration range of ZnSO4 on cell cycle and apoptosis by flow cytometry, and cell viability by MTT method in MDAMB231, HepG2 and 293 T cell lines. Fluorescent sensors NBD-TPEA and the counterstain for nuclei Hoechst 33342 were used to stain the treated cells for observing the localisation and amount of Zn(2+) via laser scanning confocal microscope. It was found that the influence manners of ZnSO4 on cell cycle, apoptosis and cell viability in various cell lines were different and corresponding to the changes of Zn(2+) content of the three cell lines, respectively. The significant increase on intracelluar zinc content of MDAMB231 cells resulted in cell death, G1 and G2/M cell cycle arrest and increased apoptotic fraction. Additionally, the mRNA expression levels of ZnT and ZIP families in the three cell lines, when treated with high concentration of ZnSO4, increased and decreased corresponding to their functions, respectively.

Temporal Expression Program of Quorum Sensing-Based Transcription Regulation in Sinorhizobium meliloti

The Sin quorum sensing (QS) system of S. meliloti activates exopolysaccharide and represses flagellum production. The system consists of an N-acyl-homoserine lactone (AHL) synthase, SinI, and at least two LuxR-type regulators, SinR and ExpR. SinR appears to be independent of AHLs for its control of sinI expression, while ExpR is almost completely dependent upon AHLs. In this study, we confirmed 7 previously detected ExpR-DNA binding sites and used the consensus sequence to identify another 26 sites, some of which regulate genes previously not known to be members of the ExpR/AHL regulon. The activities of promoters dependent upon ExpR/AHL were titrated against AHL levels, with varied outcomes in AHL sensitivity. The data suggest a type of temporal expression program whereby the activity of each promoter is subject to a specific range of AHL concentrations. For example, genes responsible for exopolysaccharide production are activated at lower concentrations of AHLs than those required for the repression of genes controlling flagellum production. Several features of ExpR-regulated promoters appear to determine their response to AHLs. The location of the ExpR-binding site with respect to the relevant transcription start within each promoter region determines whether ExpR/AHL activates or represses promoter activity. Furthermore, the strength of the response is dependent upon the concentration of AHLs. We propose that this differential sensitivity to AHLs provides a bacterial colony with a transcription control program that is dynamic and precise.

Simultaneous increase in electrical conductivity and Seebeck coefficient in highly boron-doped nanocrystalline Si

A large thermoelectric power factor in heavily boron-doped p-type nanograined Si with grain sizes ∼30 nm and grain boundary regions of ∼2 nm is reported. The reported power factor is ∼5 times higher than in bulk Si. It originates from the surprising observation that for a specific range of carrier concentrations, the electrical conductivity and Seebeck coefficient increase simultaneously. The two essential ingredients for this observation are nanocrystallinity and extremely high boron doping levels. This experimental finding is interpreted within a theoretical model that considers both electron and phonon transport within the semiclassical Boltzmann approach. It is shown that transport takes place through two phases so that high conductivity is achieved in the grains, and high Seebeck coefficient by the grain boundaries. This together with the drastic reduction in the thermal conductivity due to boundary scattering could lead to a significant increase of the figure of merit ZT. This is one of the rare observations of a simultaneous increase in the electrical conductivity and Seebeck coefficient, resulting in enhanced thermoelectric power factor.