For example, Lin excluded some participants who had participated

For example, Lin excluded some participants who had participated in >2 h/week of exercise and others with calcium intake >1,200 mg/day. Since exercise and calcium intake may be related to BMD, exclusion of these women could have

affected their findings. Moreover, women included in Lin’s study weighed less on average than those in our study (60 vs 73 kg, respectively). Our findings do mirror those of Henry et al. who observed in a sample of 68 white women that peak volumetric BMD was attained by 29 years of age [6]. We also examined peak values in black and Hispanic women and noted that these women continued to exhibit an increase in spinal BMD values until 33 years of age. However, it should be noted that we did not have data on women over age 33, so we were not able to determine if peak values occurred at 33 years or at a later point in time. If minority women continued to increase their BMD after this point, racial differences in the timing of peak values may actually be larger than we observed. BTK pathway inhibitors studies on Selleckchem DMXAA postmenopausal women have shown that Hispanic women are at lower risk of osteoporosis and fractures than whites [34, 35]. One reason

suggested for this lower risk among Hispanics is that the BMD of older Hispanic women is greater that that of whites [35, 36]. We observed, however, that white women actually have greater BMD than Hispanics at both the lumbar spine and femoral neck during adolescence. In fact, the greater BMD observed in Hispanic women as compared with whites later in life is not apparent until 29 years of age at the lumbar spine and 20 years of age at the femoral neck. This change is due to an earlier peak and more rapid decline in BMD following their

peak BMD among whites. It is most likely the continuation PJ34 HCl of this trend that places white women at much higher risk of fractures later in life than their Hispanic counterparts. Thus, it appears that one approach to osteoporosis prevention may be to determine why this rapid decline occurs among white women and attempt to slow the process during their reproductive years rather than waiting to intervene once osteoporosis has already occurred. Similar to the study conducted by Lin et al. [5], we did not observe a correlation between dietary calcium intake and BMC or BMD. This may have been the result of our study design. While most interventional studies of young healthy women have shown a correlation [37–40], longitudinal and cross-sectional studies have reported inconsistent results [26, 41–43]. A meta-analysis based on mostly cross-sectional studies showed a weak correlation coefficient (0.13) [44]. The lack of correlation between bone health and calcium intake may also have resulted from measurement error if women incorrectly reported portion sizes or types of food consumed.

067 and 0 587 ± 0 182, respectively (Fig 1E) Difference between

067 and 0.587 ± 0.182, respectively (Fig. 1E). Difference between Group1 and Group2 or Group1 and Group3 was significant (n = 3, P < 0.05). There is no difference between Group2 and Group3 (n = 3, P > 0.05). Data of the above experiments showed that the highest metastatic potential MHCC-97H cells expressed lowest level of PDCD4. The expression

level of PDCD4 was inversely correlated with the metastasis potentials of HCC cells. Plasmid construction and efficiency selleckchem of PDCD4 transfection A plasmid pcDNA3.1 (-)-PDCD4 encoding the PDCD4 gene was constructed. The recombinant was identified by double digestion with restriction enzymes and sequencing analysis. DNA sequencing of the recombinant pcDNA3.1 (-)-PDCD4 was also identified by Sangon. The efficiency of PDCD4 gene transfection was identified by western

blot analysis (Fig. 2A). Figure 2 Effects of PDCD4 on Compound C datasheet MHCC-97H cell proliferation and apoptosis. A: Western blot analysis for identification of transfection efficiency. B: MTT assay for cell proliferation. C: Flow cytometric assay for cell apoptosis. D: Hoechst 33258 staining for cell apoptosis (×200). Morphological changes of cell apoptosis were shown as chromatin condensation and nuclear fragmentation. Representative images are shown from three individual experiments. In C and D, a or Group1, b or Group 2, and c or Group3 represents cells of MHCC-97H-PDCD4, MHCC-97H-vector and MHCC-97H, respectively; d shows statistical analysis for each assay. Bars represent the means ± SD. The difference between Group1 and Group2 or Group3 was significant (P < 0.01). Effects of PDCD4 on MHCC-97H cells proliferation The MHCC-97H cell proliferation rate was assayed by MTT. The detected absorbance at 490 nm of the MHCC-97H-PDCD4 group was 0.543 ± 0.150, which was lower than that of the MHCC-97H-vector group (1.343 ± 0.268) or MHCC-97H group (1.278 ± 0.258). The difference was significant (n = 3, P < 0.05). No statistical

difference was found between the two control groups (n = 3, P > 0.05) (Fig. 2B). To further testify the Small molecule library effect of PDCD4 on proliferation of HCC cells, cell cycle analysis with a flow cytometer was performed and the proliferative indexes (PI) were calculated. As shown in Table 1, an increase of percentage both in G1 stage and in G2 stage was observed in MHCC-97H-PDCD4 cells, accompanied by a corresponding reduction in Montelukast Sodium the percentage of cells in S phase. PI was 27.83 ± 0.95%, 42.47 ± 2.90% and 44.47 ± 2.37% for the MHCC-97H-PDCD4 cells, the MHCC-97H-vector and the MHCC-97H cells, respectively. The difference of G1, G2, or S percentage and PI between the MHCC-97H-PDCD4 cells and the MHCC-97H-vector or the MHCC-97H cells is significant (n = 3, P < 0.05). No significant difference was found between the MHCC-97H-vector and the MHCC-97H cells. These data indicate that PDCD4 might promote both G1 and G2 arrest in MHCC-97H cells and further block the proliferation of HCC cells.

Apaydin I, Konac E, Onen HI, Akbaba M, Tekin E, Ekmekci A: Single

Apaydin I, Konac E, Onen HI, Akbaba M, Tekin E, Ekmekci A: Single nucleotide polymorphisms in the hypoxia-inducible factor-1alpha (HIF-1alpha) gene in human sporadic breast cancer. Arch Med Res 2008, 39 (3) : 338–345.CrossRefSelleckchem CP 690550 PubMed 15. Kim HO, Jo YH, Lee J, Lee SS, Yoon RG7112 in vivo KS: The C1772T genetic polymorphism

in human HIF-1alpha gene associates with expression of HIF-1alpha protein in breast cancer. Oncol Rep 2008, 20 (5) : 1181–1187.PubMed 16. Horree N, Groot AJ, Van Hattem WA, Heintz AP, Vooijs M, Van Diest PJ: HIF-1A gene mutations associated with higher microvessel density in endometrial carcinomas. Histopathology 2008, 52 (5) : 637–639.CrossRefPubMed 17. Konac E, Onen HI, Metindir J, Alp E, Biri AA, Ekmekci A: An investigation of relationships between hypoxia-inducible factor-1 alpha gene polymorphisms

and ovarian, cervical and endometrial cancers. Cancer Detect Prev 2007, 31 (2) : 102–109.CrossRefPubMed 18. Fransen K, Fenech M, Fredrikson M, Dabrosin C, Soderkvist P: Association between ulcerative growth and hypoxia inducible factor-1 alpha polymorphisms in colorectal cancer patients. Mol Carcinog 2006, 45 (11) : 833–840.CrossRefPubMed 19. Kuwai T, Kitadai Y, Tanaka S, Kuroda T, Ochiumi T, Matsumura S, Oue N, Yasui W, Kaneyasu AZD1390 molecular weight M, Tanimoto K, Nishiyama M, Chayama K: Single nucleotide polymorphism in the hypoxia-inducible factor-1alpha gene in colorectal carcinoma. Oncol Rep 2004, 12 (5) : 1033–1037.PubMed 20. Ollerenshaw M, Page T, Hammonds Pregnenolone J, Demaine A: Polymorphisms in the hypoxia inducible factor-1alpha gene (HIF1A) are associated with the renal cell carcinoma phenotype. Cancer Genet Cytogenet 2004, 153 (2) : 122–126.CrossRefPubMed 21. Clifford SC, Astuti D, Hooper L, Maxwell PH, Ratcliffe PJ, Maher ER: The pVHL-associated SCF ubiquitin ligase complex: Molecular genetic analysis of elongin B and C, Rbx1 and HIF-1α in renal cell carcinoma. Oncogene 2001, 20: 5067–5074.CrossRefPubMed 22. Ling TS, Shi RH, Zhang GX, Zhu H, Yu LZ, Ding XF: Common single nucleotide polymorphism of hypoxia-inducible

factor-1 alpha and its impact on the clinicopathological features of esophageal squamous cell carcinoma. Chin J Dig Dis 2005, 6 (4) : 155–158.CrossRefPubMed 23. Thakkinstian A, McElduff P, D’Este C, Duffy D, Attia J: A method for meta-analysis of molecular association studies. Stat Med 2005, 24 (9) : 1291–1306.CrossRefPubMed 24. Egger M, Davey Smith G, Schneider M, Minder C: Bias in meta-analysis detected by a simples, graphical test. BMJ 1997, 315: 629–634.PubMed 25. Bax L, Yu LM, Ikeda N, Tsuruta H, Moons KGM: Development and validation of MIX: comprehensive free software for meta-analysis of causal research data. BMC Med Res Methodol 2006, 6: 50.CrossRefPubMed 26. Bax L, Yu LM, Ikeda N, Tsuruta H, Moons KGM: MIX: comprehensive free software for meta-analysis of causal research data. Version 1.7. [http://​mix-for-meta-analysis.​info] 2008. 27.

Figure 4 LPS induces early histone H3 methylation and acetylation

Figure 4 LPS induces early histone H3 methylation and acetylation changes at the promoter region of IL-8 gene. Chromatin from HT-29 cells was harvested at the indicated time points after LPS exposure. (A) Schematic representation of IL-8 promoter region, as in Figure 3. Positions of the primers used for ChIP analyses are shown. Presented are the results of ChIP analyses using anti-acetyl-H3 Poziotinib price (B) anti-dimethyl-H3K4 (C), anti-dimethyl-H3K9

(D) and anti-trimethyl-K27 (E) antibodies. DNA sequences recovered after the indicated times of LPS treatment were quantified by real-time PCR using the primers indicated above. Average% input ± S.D from 4 independent experiments are plotted. *, p < 0.01; **, p < 0.05; n.s.= not significant, compared to control cells. Very interestingly, H3K27me3 levels were initially very low but then increased substantially starting at 6 hours and remained high 24 hours after LPS stimulation (Figure 4E). H3K27 trimethylation is catalyzed by Polycomb group (PcG) protein complexes [21, 22], which have been shown to be involved in cytokines genes

reprogramming occurring in both epithelial and macrophage cells in response to bacterial products and inflammation-related stimuli [23, 24]. It is also worth to note that when all the above ChIP assays were performed in unprimed HT-29 cells (not pre-treated with interferon-γ) we did not detect significant changes in histone H3 methylation buy MLN4924 state during the same time course (data not shown) suggesting that the observed chromatin modifications are dependent on the MD2/TLR4 pathway. However, because it

is well known that even “”pure”" LPS preparations may be contaminated with lipoproteins, we cannot selleck chemical definitively exclude that the observed chromatin modifications could be influenced by TLR2 signaling. Taken together our data indicate that while changes of H3-acetyl, H3K4me2 and H3K9me2 state in the IL-8 promoter region occur rapidly, transiently and correspond to transcription activation, the changes of H3K27me3 levels Depsipeptide occur at a later time and are long lasting. Finally it should be considered that a strong mark of gene repression, such as H3K27me3, could predispose to a more repressed state of IL-8 gene and, thus, could render the gene less responsive to further LPS stimulation. Moreover, H3K27me3 is also related to DNA hypermethylation that has been shown to occur in intestinal cancer at PcG target genes. In particular, it has been recently demonstrated that hypermethylation of PcG target genes in intestinal cancer is mediated by inflammation [24]. Thus, although our data indicate that DNA methylation is not directly involved in LPS response, such phenomenon may occur later, after prolonged exposure to LPS, as a consequence of PcG proteins recruitment at IL-8 gene.

Quantitative RT-PCR confirmed enhanced expression of s-CLU strict

Quantitative RT-PCR confirmed enhanced expression of s-CLU strictly correlated to

mRNA expression in both KF-TX and SKOV-3-TX cells when compared with their parental cell lines (Figure 2C). Table 4 List of ovarian cancer cells and their IC50 for TX in a three days GS-1101 chemical structure treatment experiment. Histological type Cell line IC50 (TX; nM) Serous KF 100 Serous KF-TX 500 Serous SKOV-3 20 Serous SKOV-3-TX 100 Serous OVK18 50 Clear cell TU-OC-1 6900 Clear cell KOC-7c 6700 Figure 2 S-CLU is up-regulated in the chemo-resistant cells: A. Western blotting analysis of CLU in a panel of ovarian cancer cells. Equal amount of proteins were loaded, resolved by SDS-PAGE NSC 683864 in vivo and immunoprobed with anti-CLU mAb. S-CLU was found in the cells and media. Some ovarian cancer cells

express relatively high levels of CLU in comparison to immortalized non tumorigenic ovarian epithelial OSE cells. B. Chemo-resistant KF-TX cells shows higher expression levels of CLU compared to parental KF cells. A similar result is found in SKOV-3 compared to SKOV-3-TX cells. C. Quantitative PCR showing the difference in CLU transcript level between the TX-sensitive and TX-resistant clones in both KF (left) and Skov-3 (right) systems. To investigate whether upregulation of s-CLU expression is a cause or a result of TX-induced resistance, both parental KF and KF-TX cells were treated with TX in a dose dependent fashion for 6 h. Sensitive KF cells rapidly responded by increasing s-CLU expression level under low doses of TX. In this experiment cellular viability mainly decreased click here when TX dose surpassed IC50. KF-TX cells already IMP dehydrogenase expressing higher CLU levels, did not further express CLU following TX treatment (Figure

3A). When we treated cells with TX up to 48 h, KF parental cells progressively increased CLU expression levels up to IC50 doses (100 nM) then CLU was down-regulated at higher doses. On the other hand, CLU expression level (already high) did not change in KF-TX cells. Again, only at doses higher than IC50 (500 nM), CLU was down-regulated (Figure 3B). S-CLU detected in cells’ medium progressively decreased up to IC50 doses in the sensitive cells suggesting its retention inside cells. However, secretion of CLU into the media by resistant cells clearly extended up to higher concentration of TX if compared with parental cells. Considering that changes in CLU expression seem independent of CLU mRNA, which did not change significantly as indicated by real-time PCR (data not shown), these results suggest that post-translational modification of CLU, including maturation and secretion, may be altered in response to TX treatment. Figure 3 Induction of CLU in a time and dose dependent fashion by TX. A. Western analysis showing s-CLU expression after 6 h treatment with TX. Induction of s-CLU is evident in chemo-sensitive KF cells when treated with high doses of TX but not in KF-TX, in which the high levels of s-CLU remained unchanged.

Eur J Pharmacol 375:261–276PubMedCrossRef”
“The 4th Internat

Eur J Pharmacol 375:261–276PubMedCrossRef”
“The 4th International symposium entitled “Current Trends in Drug Discovery Research” (CTDDR-2010) was organized in the sprit of the 1st, 2nd, and 3rd CTDDR (2001, 2004, and 2007) symposia from February 17 to 21st, 2010. The symposium had a focus on the innovative drug discovery approaches for infectious and tropical diseases (malaria, filaria, leishmania, HIV, and

tuberculosis), aging, genetic, metabolic and endocrine disorders (neurodegenerative, diabetes, obesity, CNS- and CVS- related disorders), and reproductive disorders (osteoporosis). The deliberations contained the cocktail of computational endeavors, innovative drug discovery approaches and in-depth analysis of structure-activity relationships (SAR), new drug targets and state of art techniques for the syntheses of organic molecules of biological interest. A preliminary classification of sub-areas for discussions included cellular and buy GW786034 molecular signaling, virtual library design and screening, system biology, drugs from

nature/bioimaging selleck chemical and bioprospecting, molecular approaches to disease therapy, validated therapeutic targets, drug design, synthesis, QSAR, CADD, and CAMM, novel approaches to drug discovery, pharmacokinetics/pharmaceutical sciences, translational research, informatics in drug discovery, and preclinical/clinical trials. The symposium was an outstanding success as it covered the above topics in 56 lectures delivered in 16 sessions, 280 posters presented in 4 poster sessions. It provided a platform Plasmin to about 600 researchers including 45 from other countries including USA, Germany, France, UK, Switzerland, Greece, Hungary, Denmark, Canada, South Africa, Russia, Italy, Belgium, Netherlands, Hong Kong, Japan, Egypt, Turkey, Australia

and other countries for lively interactions during the 5-day deliberations. In this special issue, a total 68 manuscripts were submitted for publication. The manuscripts were peer-reviewed by at least two experts in the field and 43 manuscripts were successful in navigating the process and were included in this particular issue of Medicinal Chemistry Research. I, as guest editor gratefully acknowledge the reviewers of manuscripts, Mr. A.S. Kushwaha for secretarial assistance, Dr. Stephen J. Cutler, his team and Birkhauser Verlag for providing all out support for successfully bringing out this special issue.”
“Introduction The acridinones represented by imidazo- and triazoloacridinones are a new group of potent antitumor compounds (Cholody et al., 1990, 1992, 1996) from which one of the most active derivatives called as C-1305 has been selected for extended preclinical trials and the other one called C-1311 (for review see Mazerska et al., 1998) is currently undergoing phase II clinical trials as drug SymadexTM (Burger et al., 1996; Den Brok et al., 2005a, b, c).

Figure 8a shows the in-plane charge density for all models In-pl

Figure 8a shows the in-plane charge density for all models. In-plane alignment does indeed have a great effect upon the charge density; A N models exhibit large low-density central regions (away from the donors) whilst B N have high-density pathways in one direction, and C N show the greatest extent of high-density regions. Figure 8 Local density of states: top-down view. (a) Charge density (all models), line-averaged along [001] and normalised such that their

values’ ranges are each [0,1]. (b) Charge densities of N ∈ 4,80 models, normalised to |Ψ2| = 1. Differences also shown, on two scales. To focus on bilayer-specific effects, N = 4 and 80 models were rescaled, and their differences are shown in Figure 8b. The electronic density reorganises as the layers approach, in a type-dependent manner. The magnitude of the rearrangement is ≤ 20% of the single-layer density. Consideration JNK-IN-8 ic50 of disorder As mentioned earlier, though the main focus of this work is perfectly ordered systems, recent attention has been given to disorder. Here, we consider how these ordered results can contribute to that discussion. As it is useful to recall which calculations have been previously performed in the literature, Table 2 summarises the state of the field and introduces terminology to distinguish between

the various models. Table 2 Listing of ab initio AC220 supplier works in this field covering systems with 1/4 ML phosphorus density Model type SZP DZP System Arrangement Bulk   filipin bulk-SZP [14, 16] bulk-DZP [16]   Ordered δ-SZP-ord [14, 16] δ-DZP-ord [16, 19] δ Disordered δ-SZP-dis [14, 23] δ-DZP-dis [23]   Mixed-pseudo δ-SZP-mix [14, 23] δ-DZP-mix [23] δ n∈2..5 Ordered   δ n -DZP-ord [19]   Ordered δ δ-SZP-ord [23] δ δ-DZP-ord a δ δ Disordered δ δ-SZP-dis [23] Intractable   Mixed-pseudo δ δ-SZP-mix [23]   δ-wire Ordered   δ-wire-DZP-ord [21]   Staggered  

δ-wire-DZP-stag [21] δ refers to a single- δ-layer system, δ n to n multiple adjacent δ layers, δδ to the bilayer systems considered here, and δ-wire to the dually confined monolayer nanowires considered in [21]. Note that further subtleties, such as the vertical separation and in-plane alignment considered here, could form a third (or fourth) tier of model nomenclature, but are omitted for brevity here. aRefers to this work. Interacting δ layers have recently been studied from the point of view that current experimental systems involve some inherent level of disorder [23]. Whilst it is recognised that a complete DZP model of interacting quasi-disordered bilayers is currently intractable (let alone incorporating disorder on any realistic scale), they offered the rational approach of contrasting a DZP model of a single quasi-disordered δ layer against an SZP model and then extending the SZP model to cover a quasi-disordered bilayer.

In addition, the species is less abundant at the one site with 10

In addition, the species is less abundant at the one site with 100 % detectability. It is difficult to compare numbers of specimens collected with previous studies due to variable effort. However, in the 1970s, numbers as high as 83 were reported from one breeding

site collection in the Cypress Creek system. Boschung (1976) estimated 800–1200 Slackwater Darter were selleck chemicals llc present in one segment of Cemetery Branch in the Cypress Creek system, where they are now presumed extirpated. Recent surveys produce numbers of specimens comparable to this at only one site, in the Cypress Creek system, and evidence indicates a decline over time at this location. Since breeding sites are targeted for sampling, it is difficult to compare detectability of non-breeding and breeding sites over time. The species was detected at four of 25

non-breeding sites during this study, however. Non-breeding sites should be included in future monitoring efforts for these species, as the potential environmental stressors in these habitats are poorly known. Although two new breeding sites were discovered during SYN-117 research buy this study, one of them is in an industrial cotton field, and it is doubtful that the seepage habitat will persist due to plowing. There are potential seepage areas in the headwaters of both the Brier Fork and Swan Creek systems, which should be explored and surveyed for Slackwater Darter during the breeding season. The decline in distribution and abundance make detection of this species difficult to monitor. At many sites, numerous samples were necessary for the detection PtdIns(3,4)P2 of Slackwater Darter, suggesting very low numbers of individuals are present relative to historical samples. Future monitoring must include multiple samples at each site to insure detection. Several environmental problems may be contributing to the decline of this species, including various types of passage barriers, habitat degradation and

the destruction of seepage areas via the construction of farm ponds. Boschung (1976) emphasized the importance of connectivity of breeding and non-breeding habitats, and gave a range of bank heights at existing breeding sites as 30–45 cm. Although it is impossible to go back and gather comparative data, data on current bank height ratios, low at extant and Tanespimycin molecular weight higher at apparently extirpated breeding sites and associated stream channels suggest that channel incision may play a role in the decline of this species at some sites. Additionally, culverts at road crossings are known passage barriers to small fishes (Boubee et al. 1999; Kemp and O’Hanlley 2010). Future conservation efforts for this species should include an evaluation of potential environmental impacts on the migration of this species. Prioritization of breeding sites for protection is also essential for the persistence of Slackwater Darter.

Furthermore, our study focussed on only

one plasmid and h

Furthermore, our study focussed on only

one plasmid and host (E. coli) combination. Although this combination is relevant, because of its high prevalence in Dutch broilers, other plasmid – host combination might exhibit different behaviour. Plasmid loss was not observed as expected because of the presence of two addiction systems, which account for stable inheritance of the plasmid to daughter cells [22]. The presence of these addiction systems is common in IncI1 plasmids [10]. The reduction of the ESBL-gene carrying plasmid shall thus depend on fitness costs involving reduced growth or maximum density of its host. Conjugation was modelled as a mass Salubrinal mouse action process, which is often used to describe the spread of infectious diseases among host individuals [23]. This mass action assumption is commonly used for modelling the conjugation

process, as it explains mechanistically that at higher concentrations of bacteria, conjugation is more efficient because cells make more frequent contacts [12, 24]. With mass action we assume that the time taken by the actual conjugation process is much smaller than the time between contacts of bacteria, which seems a valid assumption, because much higher conjugation coefficients are found with similar conjugation systems [25]. Furthermore, assuming mass action means that we assume homogeneous mixing, this is thought to occur PRN1371 molecular weight in our in vitro experiments, but might not be the case under natural conditions. When under natural conditions in the gut mixing is not homogeneous, the conjugation will be less efficient because fewer contacts are made. This might lead to a decrease of bacteria carrying the plasmid when small fitness costs exist, which cannot be measured in our in vitro experiments. For our analyses, we used a logistic growth model by Barany and Roberts [18] for which we separated the GSK126 chemical structure population into three subpopulations (D, R and T) and added conjugation and plasmid loss dynamics. The model does not describe a death phase in which the bacterial population dies out. A death phase occurs when the medium in which the populations are grown is depleted of nutrients. Such a death

phase was not observed in the experiments. Therefore, the model was appropriate to describe the MTMR9 population dynamics in our experiments. The conjugation coefficient γ T of the transconjugant was found to be much higher than that of the donor. This might be due to repression of conjugation [9, 26]. By such a mechanism conjugation becomes repressed after a certain period since acquiring the plasmid. Newly formed transconjugants have a transient period in which conjugation is de-repressed and the conjugation coefficient is higher. The population of donors might be in a repressed state such that the increase of transconjugants is slower in the beginning of the experiment, and the accumulation of new transconjugants increases the overall conjugation coefficient.

1 ≤ ϵ ≤ -0 03 Figure 3 Mechanical response of bulk PE (a) Bulk

1 ≤ ϵ ≤ -0.03. click here Figure 3 Mechanical response of bulk PE. (a) Bulk PE under simulated uniaxial tension and compression; and (b) Poisson’s ratio of bulk PE under simulated compression. Simulated compression selleck chemicals llc loading Simulated compression loadings were performed for each of the particles described in ‘Spherical particle molecular models’ section to determine the influence of particle size on the mechanical response. These simulations are similar to the type of compression loads experienced by polymer particles in ACAs when they are compressed between the flat faces of the contacts between the

chip and substrate (Figure  1). The compression was applied to the simulated particles using rigid plates above and below the particles (Figure  4a). Figure  4b shows the dimensions associated with the compression

simulations for a spherical particle of radius R. Figure 4 Applied compression using plate above and below the particles, and dimensions of the compression simulation. (a) Compression of polymer nanoparticle between two flat, rigid surfaces and (b) the dimensions associated with the model. Computational MK-0457 supplier compression tests of the modeled particles are performed by MD as illustrated in Figure  5. Two diamond plates of thickness t = 0.5 nm were placed at both the top and bottom of the particles with a gap of h 0 = 1.0 nm. Constant strain-rate loading was simulated by stepping both the plates towards the particle center, followed by structural relaxation period of 20 ps. Strain rates of 3.125 × 107 s-1 were maintained for all particle sizes by adjusting the step distance of the loading plates (see Table  2).

The temperature of the particles were kept constant by a Nosé-Hoover thermostat at T = 250 K, while the carbon atoms in the loading plates were frozen such that the atoms did not have displacements of any kind except as dictated by the controlled vertical compression. The frozen carbon atoms still maintained the usual non-bonded interactions with the particle Selleckchem Dolutegravir molecules (Table  1). This modeling process is similar to that used for silicon nanospheres [22]. Figure  5 shows the compression of the D 20 particle. Figure 5 Compressed configuration of the D 20 spherical particle. To quantify the simulated response of the polymer particles compressed by a load of P, the nominal strain and nominal stress were defined as, respectively, (1) (2) where h is the loading plate displacement from the initial contact position h 0 (Figure  4b). It is important to note that although these parameters are not strains and stresses according to their classic tensoral definitions [23], they are used herein as simple scalar measures in a manner consistent with previous studies [5, 6].