An OA may lead to an

An OA may lead to an increase in BMD as a result of increased subchondral bone formation with stiffer bone, leading to mechanical stress on cartilage during impact loading and development of subchondral sclerosis and osteophytes [14, 22]. The protective effect of this against fracture may be outweighed by the effect osteoarthritis has RAD001 clinical trial on the hip in reducing range of motion, especially rotation and

abduction/adduction, proprioception and muscle strength [6, 23] and thus increasing both the risk of falling and the risk of a fracture if a fall occurs. When comparing the non-injured side, we found more OA in the fracture patients than in the contusion patients. The difference found on the non-injured side was unexpected,

and no studies have, to our knowledge, previously reported this. Earlier studies have only investigated the injured side [5]. The results for the non-injured side should be interpreted with caution, as it is a post hoc exploratory analysis. However, a higher proportion of OA on the non-injured side in fracture patients may point to an influence on fall mechanics due to a stiffer joint with changed proprioception leading to a higher risk of fracture. The number of patients is larger on the non-injured side as we included the patients receiving a hemiarthroplasty for the analysis of the contralateral, uninjured hip. There was a tendency towards more OA on the injured side for trochanteric fractures than for femoral neck fractures with an MJS in the hips with femoral neck fractures STA-9090 in vivo of 3.72 mm compared to 3.42 mm in the trochanteric fractures and Farnesyltransferase a tendency towards more OA according to K&L in the trochanteric group (Table 2). This supports previous findings of less OA in patients with femoral neck fractures than in patients with trochanteric fractures and gives some support to claims that OA protects against femoral neck fractures, but may lead to a S63845 research buy relative increase in trochanteric fractures [5, 6, 15, 24]. The retrospective nature of this study leads to potential weaknesses. A selection

bias is a potential problem with case–control studies. However, the cases were from our prospective in-house fracture register, and the controls were all patients with the diagnosis “hip contusion” from the discharge register, and thus unselected. The patients were recruited from the community hospital area and should be representative of the general population. A strength of our study is the use of a control group. Patients with hip trauma admitted to the hospital even in the absence of a fracture are probably frail, as most patients who contuse their hip will be treated as outpatients. The ones requiring admission may have previous hip pathology, such as osteoarthritis, which may be painful when traumatized. This, however, does not seem to be the case in our patients.

The next step of our study was to give a more detailed characteri

The next step of our study was to give a more detailed characterization of the interaction of thrombin with previous (due to their action) polyphenolic compounds. The BIAcore interaction analysis system may be used to examine the influence of the compounds on each other, i.e., on proteins, in terms of specificity

of a binding reaction, kinetics and affinity. BIAcore analysis system uses surface plasmon resonance (SPR) to monitor the interaction between ABT-263 research buy molecules during the experiment time (Torreri et al., 2005). In our analysis, among the tested compounds the highest affinity to thrombin was presented by cyanidin and quercetin (Table 2). These results are in agreement with BIAcore parameters obtained by Mozzicafreddo AZD2014 in vitro et al. (2006). They observed that quercetin has the lowest K D value, whereas K D for (−)-epicatechin was the highest. Similar parameters of silybin and (+)-catechin to association thrombin, despite their clearly distinct effect on the enzyme, are probably caused by the fact that, in BIAcore analysis, compounds bind to whole protein. When a ligand binds to the part of the protein which has no

effect on its function in BIAcore, we observe the same response as in the case of binding to the enzyme active center. This Foretinib order suggests that (+)-catechin probably bind also to other places of the enzyme. Cyanidin and quercetin, in BIAcore analyses, show the strongest affinity to thrombin, which is probably even stronger than the fibrinogen and PAR receptors affinity. Therefore, it explains the inhibition of thrombin proteolytic activity caused by these compounds. Only the partial inhibition of thrombin proteolytic activity by silybin can be explained by the fact that silybin affinity

to thrombin is higher than of cyanin, catechin or epicatechin, but lower in comparison to cyanidin and quercetin. Fludarabine order Analysis of graphs plotted by the Lineweaver–Burk linearization method (Lineweaver and Burk, 1934) (Fig. 5) demonstrated a competitive nature of human thrombin inhibition by using polyphenol aglycones. This means that these compounds mimic the structure of the substrate and reversibly interact with the free form of the enzyme in competition with the substrate for the enzyme active site. When the inhibitor occupies the active center of the enzyme, it prevents binding of the substrate and abolishes product generation. This inhibition may be reduced by adding more substrate to the reaction mixture (Bjelakovic et al., 2002). Our results obtained from Lineweaver–Burk curves confirm these assumptions (Table 3). Cyanidin, quercetin, silybin, (+)-catechin and (−)-epicatechin caused an increase of Michaelis constant value, while no effect on the maximum speed of reaction and on the enzyme catalytic constant was observed. Only in the case of cyanine we observed a mixed type of inhibition.

J Bacteriol 2000,182(24):7083–7087 PubMedCrossRef 12 Moorhead SM

J Bacteriol 2000,182(24):7083–7087.PubMedCrossRef 12. Moorhead SM, Dykes GA: Influence of the sigB gene on the cold stress survival and subsequent recovery of two Listeria monocytogenes serotypes. Int J Food Microbiol 2004,91(1):63–72.PubMedCrossRef 13. Chan YC, Hu Y, Chaturongakul S, Files KD, Bowen BM, Boor KJ, Wiedmann M: Contributions of two-component regulatory systems, alternative sigma factors, and negative regulators to Listeria monocytogenes cold

adaptation and cold growth. J Food Prot 2008,71(2):420–425.PubMed 14. Oliver HF, Orsi RH, Ponnala L, Keich U, Wang W, Sun Q, Cartinhour SW, Filiatrault MJ, Wiedmann M, Boor KJ: Deep RNA sequencing of L . monocytogenes reveals overlapping and extensive stationary phase and Sigma B-dependent transcriptomes, including multiple highly transcribed see more noncoding RNAs. BMC Genomics 2009, 10:641–2164–10–641.CrossRef 15. Abram F, Starr E, Karatzas KA, Matlawska-Wasowska K, Boyd A, Wiedmann M, Boor KJ, Connally D, O’Byrne CP: Identification of components of the Sigma B regulon in Listeria monocytogenes that contribute to acid and salt tolerance. Appl Environ

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Environ Microbiol 2008,74(3):594–604.PubMedCrossRef Selleck MK-8931 17. Rea RB, Gahan CG, Hill C: Disruption of putative regulatory loci in Listeria monocytogenes demonstrates a significant role for Fur and PerR in virulence. Infect Immun 2004,72(2):717–727.PubMedCrossRef 18. Mattila M, Somervuo P, Rattei T, Korkeala H, Stephan R, Tasara T: Phenotypic and transcriptomic analyses of Sigma L-dependent characteristics in Listeria monocytogenes EGD-e. Food Microbiol 2012,32(1):152–164.PubMedCrossRef 19. Okada Y, Okada N, Makino S, Asakura H, Yamamoto S, Igimi S: The sigma factor RpoN (sigma54) is this website involved in osmotolerance in Listeria monocytogenes . FEMS Microbiol Lett 2006,263(1):54–60.PubMedCrossRef 20. Raimann E, Schmid B, Stephan R, Tasara T: The alternative sigma factor Sigma(L) of L . monocytogenes promotes BCKDHA growth under diverse environmental stresses. Foodborne Pathog Dis 2009,6(5):583–591.PubMedCrossRef 21. Robichon D, Gouin E, Debarbouille M, Cossart P, Cenatiempo Y, Hechard Y: The rpoN (sigma54) gene from Listeria monocytogenes is involved in resistance to mesentericin Y105, an antibacterial peptide from Leuconostoc mesenteroides . J Bacteriol 1997,179(23):7591–7594.PubMed 22. Arous S, Buchrieser C, Folio P, Glaser P, Namane A, Hebraud M, Hechard Y: Global analysis of gene expression in an rpoN mutant of Listeria monocytogenes . Microbiology 2004,150(Pt 5):1581–1590.PubMedCrossRef 23.

In this attempt, we run into a previously described phenomenon th

In this attempt, we run into a previously described phenomenon that may become a source of erroneous results. If toxins are expressed from the arabinose-inducible P BAD promoter and antitoxins from an IPTG-inducible promoter, MDV3100 it is important to consider that

IPTG inhibits P BAD directly [71]. When we used an expression vector that encoded for the IPTG-insensitive C280* version of AraC transcriptional activator, we could not see any cross-inhibition. Based on that, a recent report on functional non-cognate TA interactions in Mycobacterium tuberculosis[67] may require retesting. Selective targeting of mRNA by toxins as a mechanism of gene regulation In the current study, we found that the cleavage products produced by TA toxins differ in stability. Selective targeting of mRNAs by endoribonucleolytic toxins and different ZD1839 stabilities of the resulting cleavage products may constitute another layer of gene regulation in the bacterial stress response. Differences in half-life and translational efficiency of mRNA cleavage products, along with generation of a pool of ribosomes

lacking the anti-Shine-Dalgarno sequence (as shown for MazF [22]), could profoundly affect the proteome composition. An example of such an effect is the occurrence of a MazF-resistant protein pool in E. coli[72]. The accumulation of toxin-encoding mRNA fragments may have potential use as a marker of toxin activation in studies of stressed and non-growing bacteria. Increase Cell press of the JNK assay T/A ratio may possibly trigger a positive feedback loop consisting of transcriptional activation of the TA operon, successive cleavage of the TA transcript, buildup of the toxin-encoding mRNA fragments, and translation of them, shifting the T/A balance (Figure 7). Thus, it can be related to TA-linked growth heterogeneity in bacterial populations (Additional file 1: Figure S6) [38, 39,

54]. Conclusions The main finding of this study is that bacterial toxin-antitoxin systems affect mutually each others’ expression and activity (Figure 7). We show that overexpression of one toxin can activate transcription of the other TA operons. Toxins with endoribonuclease activity add another layer of complexity to these interactions. They cleave TA mRNA, which is followed by degradation of the antitoxin-encoding RNA fragments and accumulation of the toxin-encoding fragments. We show that these accumulating mRNA fragments can be translated to produce more toxin. Most of bacteria have many different TA systems. Although their function is debatable, many TA toxins have similar activity and the inhibitory effect on bacterial cells is common to all of them. Therefore, an important question is whether TA systems are redundant or not. Another intriguing issue is whether different TA systems are functionally connected and do cross-talk [44, 70]. Here we over-expressed toxins to show that TA systems have a potential to form a network of cross-reacting regulators in E. coli.

Cell Signal 2010, 22:234–246 PubMedCrossRef 25 Guo JP, Pang J, W

Cell Signal 2010, 22:234–246.SBI-0206965 price PubMedCrossRef 25. Guo JP, Pang J, Wang XW, Shen ZQ, Jin M, Li JW: In vitro screening of traditionally used

medicinal plants in China against enteroviruses. World J Gastroenterol 2006, 12:4078–4081.PubMed 26. Rahaus M, Desloges N, Wolff MH: Replication of varicella-zoster virus is influenced by the levels of JNK/SAPK and p38/MAPK activation. J Gen Virol 2004, 85:3529–3540.PubMedCrossRef 27. Wei L, Zhu Z, Wang J, Liu J: JNK and p38 mitogen-activated protein kinase pathways contribute to porcine circovirus type 2 infection. J Virol 2009, 83:6039–6047.PubMedCentralPubMedCrossRef 28. Meng Q, Xia Y: c-Jun, at the crossroad of the signaling network. Protein Cell 2011, 2:889–898.PubMedCrossRef 29. Dey N, Liu T, Garofalo RP, Casola A: TAK1 regulates NF-KappaB and AP-1 activation in airway epithelial cells following RSV infection. Virology 2011, 418:93–101.PubMedCentralPubMedCrossRef 30. Huang HI, Weng KF, Shih SR: Viral and host factors that contribute to pathogenicity of enterovirus 71. Future Microbiol 2012, 7:467–479.PubMedCrossRef 31. Takeuchi O, Akira S: Innate immunity to virus infection. Immunol Rev 2009, 227:75–86.PubMedCrossRef 32. Hou W, Gibbs JS, Lu X, Brooke CB, Roy D, Modlin RL, Bennink JR, Yewdell JW: Viral infection triggers rapid differentiation of human blood monocytes into dendritic cells. Blood 2012, 119:3128–3131.PubMedCentralPubMedCrossRef 33. Lin YW, Wang SW,

Tung YY, Chen SH: Enterovirus 71 infection of human dendritic cells. Exp Biol Med (Maywood) 2009, 234:1166–1173.CrossRef 34. Dejnirattisai W, Duangchinda T, Lin CL, Vasanawathana S, Jones M, Jacobs M, Malasit P, Xu XN, Screaton G, Mongkolsapaya J: A complex interplay among virus, dendritic cells, T cells, and cytokines in dengue virus infections. J Immunol 2008, 181:5865–5874.PubMedCrossRef 35. Ceballos-Olvera I, Chavez-Salinas S, Medina F, Ludert JE, del Angel RM: JNK phosphorylation, induced during dengue virus infection,

is important for viral infection and requires the presence of cholesterol. Virology 2010, 396:30–36.PubMedCrossRef 36. Bryk D, Olejarz W, Zapolska-Downar D: Mitogen-activated protein kinases in atherosclerosis. Postepy Hig Med Carteolol HCl Dosw (Online) 2014, 68:10–22.CrossRef 37. Waetzig V, Czeloth K, Hidding U, Mielke K, Kanzow M, Brecht S, Goetz M, Lucius R, Herdegen T, Hanisch UK: c-Jun N-terminal kinases (JNKs) mediate pro-inflammatory actions of microglia. Glia 2005, 50:235–246.PubMedCrossRef 38. Sukhumavasi W, Egan CE, Denkers EY: Mouse neutrophils require JNK2 MAPK for Toxoplasma gondii-induced IL-12p40 and CCL2/MCP-1 release. J Immunol 2007, 179:3570–3577.PubMedCrossRef 39. Turner NA, Warburton P, O’Regan DJ, Ball SG, Porter KE: Modulatory effect of interleukin-1alpha on expression of structural matrix proteins, MMPs and TIMPs in human cardiac myofibroblasts: role of p38 MAP kinase. Matrix Biol 2010, 29:613–620.PubMedCentralPubMedCrossRef 40.

There were increases from baseline during treatment in both group

There were increases from baseline during treatment in both groups. MMRM analysis showed that the increases in finite element strength and normalized axial compression strength at 18 months were significantly higher in the teriparatide group compared with the risedronate group (p ≤ 0.05). The between-treatment differences were not statistically significant at 6 months (Table 1). Similar results were observed for stiffness (data not shown). Table 1 Finite element strength in the different loading modes (anterior bending, axial compression, axial torsion) and normalized axial compression strength for the teriparatide and risedronate treatment groups Variable

Time (months) Teriparatide Risedronate p value a n Mean (SD) n Mean (SD) Finite element strength Anterior bending (kN mm) this website Baseline 36 94.7 (41.8) 36 96.2 (42.3) – 6 see more 25 121.3 (49.9) 32 113.5 (46.0) 0.661 18 29 140.2 (58.8)b 31 112.8 (40.8) 0.012 Axial compression (kN) Baseline 36 5.07 (2.33) 37 4.90 (2.28) – 6 25 6.21 (2.87) 33 5.81 (2.23) 0.547 18 31 7.08 (3.48)b 31 5.95 (2.2) 0.015 Axial torsion (kN mm) Baseline 36 48.4 (22.1) 37 48.6 (21.2)

– 6 25 62.4 (26.3) 33 57.9 (20.9) 0.548 18 31 71.0 (31.8)b 31 58.2 (19.2) 0.005 Normalized axial compression strength (N/mm2)   Baseline 36 4.50 (2.20) 37 4.41 (2.16) – 6 25 5.32 (2.71) 33 5.25 (2.18) 0.677 18 31 6.13 (3.29)b 31 5.38 (2.08) 0.021 a p value for Selleckchem SCH727965 between group comparison bChange from baseline within groups (p < 0.05) from a mixed model repeated-measures analysis of changes from baseline including fixed effects for treatment, visit and the interaction between treatment and visit, and random

those effects for patients nested within treatment, plus the following covariates: age, baseline PINP, fracture <12 months before study, duration of prior bisphosphonate use, screening GC dose, and cumulative GC dose prior to and during study. MMRM sample sizes for changes from baseline to 6 months (n = 23), and to 18 months (n = 28) for Teriparatide; and baseline to 6 months (n = 28), and to 18 months (n = 28) for Risedronate Correlations between changes in bone turnover markers and changes in FEA variables Table 2 presents the Spearman correlation coefficients between the absolute changes from baseline of PINP at 3, 6 and 18 months and the absolute changes from baseline in FEA parameters at 18 months of therapy in the teriparatide and risedronate groups. Significant positive correlations between the change in PINP at 3, 6 and 18 months with the changes in finite element strength and stiffness in all loading modes at 18 months (anterior bending, axial compression, and axial torsion) and in the change in normalized axial compression strength were observed in the teriparatide group (r = 0.422 to r = 0.563).

falciparum populations (e g , [34]) For example, the fact that t

falciparum populations (e.g., [34]). For example, the fact that the same conserved set of HBs can describe var sequence diversity at multiple geographic

scales and locations reveals strong balancing selection to maintain ancient sequence fragments across vast expanses of time and space. The complex BX-795 mouse ecological and evolutionary dynamics that are at play warrant further study because they likely shape P. falciparum antigenic diversity, and in so doing, strongly impact the epidemiology of malaria. Acknowledgements We thank Donald selleck compound S. Chen and Yael Artzy-Randrup for helpful input related to this work. MP is an Investigator at Howard Hughes Medical Institute. EBB was supported by a Department of Energy Computational Science Graduate Fellowship (grant DE-FG02-97ER25308). Electronic supplementary material Additional file 1: Additional figures. Figure S1. Respiratory distress (RD) as a function of host age and rosetting. Figure

S2. HB composition of known rosetting var genes. Figure S3. Linkage disequilibrium coefficient (D) values for all pairs of HBs in the genomic dataset. Figure S4. Community partition of weighted linkage network of HBs. Figure S5. HB-HB expression rate correlation matrix. Figure S6. Model of respiratory distress. Figure S7. Relationship between rosetting and respiratory distress. Figure S8. Relationship between impaired consciousness and the expression of various var types and HBs. Figure S9. The best fit relationship between six variables and rosetting using a window analysis. Figure S10. Relationship between rosetting and expression rates of var types and HBs. Figure S11. PC-classic var type association network. Figure S12. PC-HB relationships. Figure S13. Principal components in data space. Figure S14. The amount of variation explained by each PC. Figure S15. PCA for mafosfamide two subsets of the data. Figure S16. Representation of select homology blocks. Figure S17. HB-classic var type association network. (PDF 11 MB) Additional file 2: Further explanation of methods. (PDF 59 KB) Additional

file 3: Additional tables. Table S1. Multiple regression models of rosetting that include an HB expression rate as an independent variable. Table S2. Multiple regression models of rosetting that include an HB expression PC as an independent variable. Table S3. Statistics for multiple regression models predicting rosetting with and without age. (PDF 711 KB) References 1. Chan JA, Howell KB, Reiling L, Ataide R, Mackintosh CL, Fowkes FJ, Petter M, Chesson JM, Langer C, Warimwe GM, et al.: Targets of antibodies against plasmodium falciparum-infected erythrocytes in malaria immunity. J Clin Invest 2012,122(9):3227–3238.PubMedCrossRef 2. Chen DS, Barry AE, Leliwa-Sytek A, Smith TA, Peterson I, Brown SM, Migot-Nabias F, Deloron P, Kortok MM, Marsh K, et al.

2008) In this context it is unfortunate that we do not yet under

2008). In this context it is unfortunate that we do not yet understand the ecological significance of the extinction of the regional Pleistocene megafauna. Humans and their dogs (domesticated elsewhere ~40 ka) are associated with the extinction or widespread extirpation of >20 species of mammals including proboscideans, rhinoceroses, hippopotamus, tapirs, hyaenas, giant pangolin, AG-881 giant panda, river dolphins, and the giant primates, Pongo and Gigantopithecus. LY3039478 mw Unfortunately, the events are still too poorly documented to discuss either causes or ecological consequences (Louys 2007; Louys et al. 2007; Corlett 2009a). However, the communities in which the extirpated species lived have not collapsed and for conservationists

the real worries are not the losses of individual species but the more far-reaching effects of ecosystem collapse. The best defense against such catastrophe in Southeast Asia is to reduce human population growth and the rate of

habitat conversion and create the largest possible array of protected areas (Sodhi and Brook 2006; Corlett 2009a; Berry et al. 2010). Reserve size is especially important for terrestrial communities like the montane forests that are expected selleck to shrink in size or disappear as the climate warms. Unfortunately, the reserves that we would recommend for today’s conditions are not the same as those we will need after 100 years of projected habitat loss and climate change (Lee and Jetz 2008). Human biogeography: growing threats to regional biodiversity and ecosystems Humans have been part of nature in Southeast Asia

for a very long time. Homo erectus walked out of Africa ~1.9 Mya and spread as far as China, Vietnam, Java and Flores. They lived as small bands of hunter-gatherers who made stone tools. We do not yet know what impact they had on Pleistocene vegetation and megafauna but they used fire for the last 800 ka. H. erectus was replaced in the last hundred thousand years by populations Glutamate dehydrogenase of H. sapiens that left Africa ~85 ka. H. sapiens followed the same coastal route to Southeast Asia, arriving ~75 ka and subsequently spread to China and Australia. There is little physical evidence of this history as sea levels 70–80 ka were 50–60 m below today’s (Fig. 3b) and the traces are now submerged. The genetic evidence, on the other hand, is strong and documents the exodus from Africa, the route taken, the origins of the surviving descendants of the first wave of beachcombers in Southeast Asia, and the current patterns of diverse population distribution and admixture (Oppenheimer 2004; Hill et al. 2006). Beginning at the end of the LGM, ~19 ka, the coastal populations would have been pushed slowly inland for 12,000 years as sea levels rose from −130 m to +2–5 m, 4,200 years ago. Corlett (2009a) has reviewed the subsequent ecological impacts of these humans. They began spreading up the river valleys and practiced swidden agriculture at least 5,000 years ago.

e a tenfold increase in island size was not associated with any

e. a tenfold increase in island size was not associated with any change in single-island endemic species richness). Figure 2 also shows that the slope of the species–area relationship was steeper for island endemics than for total species richness. The same qualitative differences are also observed for the relationship

between species richness and elevation (data not shown). Fig. 2 The species–area relationship for total species richness (circles) and for single-island endemic species richness only (squares). Each point represents an island Discussion In our study we examined the endemic species richness in 201 islands and islets in the Aegean archipelago, a continental archipelago where

distance from the mainland is no more than 260 km and with continuous human presence documented over several millennia. Under these conditions, isolation AZD8931 mw should be examined with caution. However, this archipelago supports hundreds of endemic species (310 single-island endemic species were included in this study). Single-island endemic species constitute about 10% of the flora of Crete (Turland et al. 1993; Jahn and Schönfelder 1995; Turland and Chilton 2008). For the remaining 18 islands with single-island endemics, these constitute up to 2.5% of the island flora. Only large (island area more than 4.62 km2) and high (maximum elevation more than 355 m asl with the exception of one island with only 27 m) islands host single-island endemic species. Continuous human presence on an island does not seem to be related to single-island endemism,

since all 19 islands with such local endemics also support permanent human PLEKHB2 settlements. Isolation from the mainland by large stretches of sea is similarly not a prerequisite for the presence of single-island endemics. Evvoia, a large island separated from the mainland by a narrow strait of only 100 m, supports 42 single-island endemic species. Scaling up from single-island endemics to island group endemics and further to regional endemics, the minimum area values decrease. Even very small islands with an area of 1250 m2 support regional endemic species, but no single-island endemics. Perhaps the existence of endemics on such small islands and islets may be due to a metapopulation type phenomenon. Very small islands often have a high species turnover (Panitsa et al. 2008) and do not support long-term safe habitats where a single small population of a local endemic species can persist over long periods, however, these islands are recolonizable by endemic species from other islands. These endemics form part of a group of small island IDO inhibitor specialists in the Aegean (that also include non-endemics), which were discussed and listed in Rechinger and Rechinger-Moser (1951) and by Bergmeier and Dimopoulos (2003).

The atomic structure of the Ohtake model is shown in Figure 1b F

The atomic structure of the Ohtake model is shown in Figure 1b. Figure 1 Basics of the GaAs(001)-4 × 6 surface. (a) A LEED pattern using an electron energy of 51 eV, (b) atomic structure proposed by Ohtake et al. (adapted from [17]. copyright 2004 American Physical Society), and (c) As 3d and Ga 3d core-level Vorinostat purchase photoemission

spectra with various emission angles (θ e). Figure 1c displays the As 3d and Ga 3d core-level spectra of a clean Ga-rich n-GaAs(001)-4 × 6 surface taken in various angles from the normal emission to 60° off-normal emission. The excitation photon energies were set at 85 and 65 eV for As and Ga states, respectively. The estimated escape depth is Androgen Receptor Antagonist approximately 0.3 to 0.5 nm. A visual inspection of the As (Ga) 3d photoemission data identifies a feature bulged out at low (high) binding energy, suggesting that the line shape contains components in addition to the main bulk line. In fact, deconvolution of the As 3d core-level spectrum shows four components. Accordingly,

we set up a model function with four spin-orbit pairs as well as a power-law background and a plasmon- or gap-excitation-energy loss tail. The background and loss tail are represented by least squares adjustable parameters that are included AG-881 manufacturer in the model function. The background is represented by four parameters: a constant, a slope, and a power-law that is quite successful in representing the degraded electrons from shallower levels. In the energy range of the 3d spectra, the loss tail is almost entirely due to electron-hole pair excitations in the semiconductor. In GaAs, there are none that are smaller than the 1.42-eV bandgap, which implies that almost all of the line structure remains unaffected

by the loss tail. Background subtraction prior to fitting meets with a fundamental objection. It destroys the statistical relationship between the number of counts in the data point and its uncertainty, BCKDHA preventing χ 2 from reaching unity for a perfect fit and interfering with the assessment of the quality of the fit. The fact that the resolved components in the deconvolute exhibit nearly equal widths suggests that the lifetime is the same for all components. The residual differences in width are presumably due mainly to small differences in the phonon or inhomogeneous broadening of bulk and surface components. It is worth noting that a reliable least squares adjustment is readily obtained provided the model function has a multi-parameter global minimum. A multitude of unconstrained width parameters tend to produce local minima defining erroneous, unphysical parameter values. The width parameters were accordingly constrained as needed. The representative fit to the As and Ga 3d states of the clean GaAs(001)-4 × 6 surface are shown in Figure 2.