text:
- Research article
- Open Access
- Open Peer Review
Potential of novel Mycobacterium tuberculosis infection phase-dependent antigens in the diagnosis of TB disease in a high burden setting
© Chegou et al; licensee BioMed Central Ltd. 2012
- Received: 2 August 2011
- Accepted: 20 January 2012
- Published: 20 January 2012
Confirming tuberculosis (TB) disease in suspects in resource limited settings is challenging and calls for the development of more suitable diagnostic tools. Different Mycobacterium tuberculosis (M.tb) infection phase-dependent antigens may be differentially recognized in infected and diseased individuals and therefore useful as diagnostic tools for differentiating between M.tb infection states. In this study, we assessed the diagnostic potential of 118 different M.tb infection phase-dependent antigens in TB patients and household contacts (HHCs) in a high-burden setting.
Antigens were evaluated using the 7-day whole blood culture technique in 23 pulmonary TB patients and in 19 to 21 HHCs (total n = 101), who were recruited from a high-TB incidence community in Cape Town, South Africa. Interferon-gamma (IFN-γ) levels in culture supernatants were determined by ELISA.
Eight classical TB vaccine candidate antigens, 51 DosR regulon encoded antigens, 23 TB reactivation antigens, 5 TB resuscitation promoting factors (rpfs), 6 starvation and 24 other stress response-associated TB antigens were evaluated in the study. The most promising antigens for ascertaining active TB were the rpfs (Rv0867c, Rv2389c, Rv2450c, Rv1009 and Rv1884c), with Areas under the receiver operating characteristics curves (AUCs) between 0.72 and 0.80. A combination of M.tb specific ESAT-6/CFP-10 fusion protein, Rv2624c and Rv0867c accurately predicted 73% of the TB patients and 80% of the non-TB cases after cross validation.
IFN-γ responses to TB rpfs show promise as TB diagnostic candidates and should be evaluated further for discrimination between M.tb infection states.
- Receiver Operating Characteristic
- Tuberculin Skin Test
- Peptide Pool
- Receiver Operating Characteristic Analysis
- General Discriminant Analysis
The diagnosis of tuberculosis (TB) disease remains a challenge in resource-limited settings. This is particularly due to limitations in sputum smear microscopy [1], the cheapest and widely used test in such settings. Several attempts have been made towards the development of better diagnostic tests for TB [1]. The most significant development in the field has been the introduction of the automated real-time sputum processing molecular beacon assay, XpertMTB/RIF assay (Cepheid Inc., CA, USA) [2] into clinical practice but the relatively high operating costs preclude its use in resource-poor settings which often suffer from the highest TB burdens [3]. Furthermore, the dependence of most of these tests on sputum implies that they are not suitable for patients with difficulties in providing good quality sputum samples such as children, extrapulmonary TB cases, or in cases where the sputum itself is negative (for example, many patients with HIV-Mycobacterium tuberculosis (M.tb) co-infections). Immunodiagnostic assays might hold promise in such cases [4] especially if they can be developed into point-of-care tests.
One of the most notable advances in the development of immunodiagnostic tools for M.tb has been the advent of the interferon gamma release assays (IGRAs). Commercially available IGRAs include the ELISA-based Quantiferon TB Gold assays (Cellestis, Victoria, Australia) and the ELISPOT-based T SPOT.TB test (Oxford Immunotec, Abington, UK). Notwithstanding the proven usefulness of these assays in the diagnosis of M.tb infection, especially in comparison to the tuberculin skin test (TST) [5–7], an important limitation of the tests is that they do not discriminate between latent M.tb infection (LTBI) and active TB disease. This implies limited utility in high-burden settings where the prevalence of LTBI is usually high. In order to develop T cell-based assays for the diagnosis of active TB, it is imperative to identify new host markers expressed in response to established M.tb-dependent antigens, such as those used in IGRAs (ESAT-6, CFP-10, TB7.7), or novel M.tb antigens uniquely recognized by patients with active TB or LTBI.
In response to the continued pressure mounted by host immune responses in the course of M.tb infection, the bacterium is believed to respond by self-regulating the expression of many genes [8, 9]. Using in vivo and in vitro models believed to mimic the conditions encountered within the host by the tubercle bacillus as infection progresses from latency to active disease, investigators have been able to identify infection phase-dependent genes with diagnostic potential [10, 11]. In the present study, we assessed the potential diagnostic utilities of 118 M.tb infection phase-dependent antigens in TB patients and household contacts (HHCs) in a high-TB burden population. As part of a large ongoing TB biomarker study, we investigated the antigens in a 7-day diluted whole blood assay for their diagnostic potential for active TB.
Study subjects
Participants were recruited from the Ravensmead/Uitsig community in Cape Town, South Africa, as part of an ongoing Bill and Melinda Gates Foundation funded Grand Challenges in Global Health (GC6-74) study (http://www.biomarkers-for-tb.net/). Participants included in this study were enrolled between October 2006 and April 2007. All TB patients were self-reporting, untreated cases with a first episode of TB and were acid fast bacilli (AFB) positive on two sputum smears. HHCs had been living in the same house as an adult TB case who was diagnosed not more than 2 months before recruitment of the contact. All HHCs had antero-posterior view chest X-rays and assisted sputum samples taken. The X-rays were all evaluated as normal and the sputum samples found negative for AFB. Demographic data was collected on all participants and a clinical questionnaire completed. All participants tested negative with an HIV rapid test (Abbot Determine™ HIV 1/2; Abbott, Wiesbaden, Germany). Inclusion criteria for all participants were: age between 18 and 60 years, willingness to undergo HIV testing and to give written informed consent for participation in the study. Exclusion criteria for all participants included HIV infection, previous or current TB treatment, participation in a drug or vaccine trial at or within the 6 months preceding recruitment, other chronic illnesses and pregnancy. At enrolment, 10 ml of heparinized blood was collected from all participants and transported within 2 h of collection to the laboratory where a 7-day whole blood assay (WBA) (described below) was performed. Ethical approval for the study was obtained from the Committee for Human Research of the University of Stellenbosch.
A total of 118 M.tb infection phase-dependent antigens (112 recombinant proteins and 8 peptide pools) were evaluated in the study. Eight of these antigens (ESAT-6/CFP-10 fusion protein (ESAT-6/CFP-10fp), TB10.4 (Rv0288), TB10.3 (Rv3019c), TB7.7 (Rv2654c), Ag85A (Rv3804c), Ag85B (Rv1886c), HSP65 (Rv0440), ESAT-6(Rv3875)), were well-characterized TB antigens and were evaluated as "control antigens". Fifty-one antigens were DosR-induced antigens, 23 were reactivation antigens, 5 were rpfs, 6 were starvation antigens (other than Rv2654c) and the other 24 are known to be associated with stress conditions (Additional file 1: Tables S1, Additional file 2: Table S2, Additional file 3: Table S3, Additional file 4: Table S4, Additional file 5: Table S5, Additional file 6: Table S6). One of the peptide pools (Rv2659) was evaluated in three separate pools (pools A-C) while Ag85A and Ag85B were evaluated together in culture. With the exception of ESAT-6 and Rv3407, all the recombinant proteins were produced at Leiden University Medical Center (LUMC), The Netherlands. Recombinant ESAT-6 and all peptide pools were from SSI, and Rv3407 from the Max Plank Institute for Infection Biology (Berlin, Germany).
For the antigens that were available as peptide pools, there were 6 to 13 peptides in each pool. Each of the peptides was 15 amino acids long. There were eight amino acid overlaps between the peptides in each pool (Additional file 7: Table S7).
Recombinant antigens were produced as previously described [12]. Briefly, M.tb genes were amplified by PCR from genomic DNA of M.tb and cloned using the Gateway technology platform (Invitrogen, Carlsbad, CA) with pDEST17 expression vector containing an N-terminal histidine tag (Invitrogen). Sequencing was performed on selected clones to confirm identity of all cloned DNA fragments. Recombinant proteins were over expressed in E. coli BL21(DE3) and purified as described to remove any traces of endotoxin. Each purified recombinant protein was analyzed by 12% SDS-PAGE followed by Coomassie Brilliant Blue staining and Western-blotting with an anti-His antibody (Invitrogen) to confirm size and purity. Endotoxin contents were below 50 IU/mg recombinant protein as tested using a Limulus Amebocyte Lysate (LAL) assay (Cambrex, East Rutherford, NJ), and less than 0.1 IU/mg in some cases. Recombinant proteins were tested to exclude protein non-specific T cell stimulation and cellular toxicity in IFN-γ release assays using PBMC of in vitro PPD-negative, healthy Dutch donors recruited at the Blood bank Sanquin, Leiden, The Netherlands. None of these controls had experienced any known prior contact with TB patients.
Whole blood assay
Antigens were evaluated at a final concentration of 10 μg/ml as previously described [13]. Briefly, antigens were reconstituted as instructed by the respective manufacturers, to a concentration of 20 μg/ml, after which they were aliquoted into 96-well U-bottom plates (100 μl per well) in triplicates. Antigen plates were then frozen at -80°C until the day of WBA. On the day of WBA, antigen plates were thawed and 100 μl of 1 in 5 diluted whole blood [diluted with pre-warmed (37°C) medium (RPMI 1640 containing L-glutamine) (Sigma)], was added to the antigen and control wells. Plates were then incubated until day 7 in a humidified, 5% CO2, 37°C incubator. 150 μl of supernatant was harvested from each of the three antigen/control wells, pooled in a micro centrifuge tube (total of 450 μl per antigen per study participant), divided into 3 aliquots and frozen at -80°C until further use. The unstimulated control wells received medium without antigen while the positive control wells received phytohaemagglutinin (PHA) (Sigma) at 0.5 μg/ml.
IFN-γ ELISA
ELISAs were performed using a pair of monoclonal antibodies from BD Pharmingen™, (BD Biosciences). Briefly, 96-well flat-bottomed micro-titre plates (Nunc) were coated with 2 μg/ml (50 μl) of the purified mouse anti-human IFN-γ monoclonal capture antibody (diluted in 0.1 M NaHCO3). After overnight incubation at 4°C, plates were washed and blocked with 10% heat-inactivated fetal calf serum (150 μl) in phosphate buffered saline for 2 h (room temperature). After another wash, serial dilutions of recombinant human IFN-γ standard (BD Pharmingen™), and the samples (100 μl per well), were added to the designated wells, and plates incubated overnight at 4°C. Plates were then washed and 1 μg/ml (100 μl) of the biotinylated mouse-anti-human IFN-γ detection antibody (BD Pharmingen™) added. After 1 h incubation (room temperature) and a further wash, 2.5 μg/ml (100 μl) of streptavidin peroxidase (Sigma) was added to all wells, followed by addition of the substrate (O-phenylene diamine-dihydrochloride [Sigma]) (200 μl/well). Plates were then incubated in the dark for 25 mins and the optical densities read at 450 nm. All samples, standards and controls were assayed in duplicate. IFN-γ concentrations were calculated from a four-parameter logistic curve using the microplate manager software (Bio Rad Laboratories). A PHA-stimulated internal positive control supernatant (evaluated on all plates to assess the variability of the ELISA assay) had an average interplate coefficient of variation of 3.6% (95% confidence interval, 2.7-4.6%).
Although the ELISA used in our study has been used in other published studies [13–15], the standard curve for the assay ranged from 31-4000 pg/ml and many of the responses elicited by the antigens we have tested fell below the lowest point on the curve. To verify our observations, we re-evaluated the supernatants from promising antigens by a commercially available IFN-γ ELISA kit (Quantiferon TB Gold (QFT) ELISA, Cellestis, Australia). According to the manufacturer, the detection limit of the QFT ELISA is 0.05 IU/ml (about 2 pg/ml). The validation ELISA (QFT ELISA) was performed according to the manufacturer's instructions.
Statistical analysis
IFN-γ responses obtained with the Quantiferon ELISA (in IU/ml) were converted to pg/ml by multiplying by 40 [16]. Differences in IFN-γ levels elicited by the antigens were evaluated by the Mann Whitney U test for nonparametric data analysis. Optimal cut-off levels for differentiating between TB disease and no TB were ascertained by receiver operating characteristics (ROC) analysis using the "R" statistical programming language. The predictive abilities of combinations of antigens to differentiate between TB disease and no TB was investigated by performing best subsets general discriminant analysis (GDA), with leave-one-out cross validation as described previously [17]. A 5% significance level was used as guideline for determining significant associations. The data were analyzed using the Statistica 8 software, (Statsoft, Ohio, USA) and GraphPad prism, version 5.00 for Windows (GraphPad Software, San Diego, California, USA).
A total of 124 participants, 23 TB patients and 101 HHCs were enrolled in the study. The mean (± standard deviation) age of participants was 31.7 (± 15.3) years and 76 (61.3%) were female. Although neither IGRA nor TST results were available for the HHCs, it is known from our previous studies that 78-89% of adult HIV-negative TB HHCs from the study community are TST positive (10 mm cut-off) with a mean TST induration of about 23 mm [5, 13, 17]. All the antigens (n = 118) were evaluated in all TB patients (n = 23) and in groups of 19 to 21 HHCs. Because of the large number of antigens evaluated in the study, only antigens for which reportable data was generated are shown in the results section of the main manuscript. The diagnostic accuracy data for all the other antigens is shown in Additional file 8: Table S8 and Additional file 9: Figure S1. The detailed description of all the antigens evaluated in the study is shown in Additional file 1: Table S1, Additional file 2: Table S2, Additional file 3: Table S3, Additional file 4: Table S4, Additional file 5: Table S5, Additional file 6: Table S6, Additional file 7: Table S7.
IFN-γ responses in assay controls
The median IFN-γ concentration detected in the unstimulated control supernatants in both TB patients and HHCs was 0 pg/ml (range 0.0-4.3 pg/ml in TB patients and 0.0-585.4 pg/ml in HHCs). There was no significant difference in the unstimulated IFN-γ responses between the TB patients and HHCs (p = 0.10). The median IFN-γ concentration detected in PHA-stimulated supernatants in HHCs (1331.0 pg/ml, range, 0.0 to > 4000 pg/ml), was significantly higher than that observed in TB patients (326.6 pg/ml, range, 0.0 to > 4000 pg/ml) (p = 0.01), as previously observed [18]. The IFN-γ response obtained for the unstimulated control for each participant was subtracted from all antigen/control-stimulated levels before further analysis of the data.
IFN-γ production in response to classical TB antigens
Eight M.tb classical antigens (Additional file 1: Table S1) were evaluated in this study. TB10.4 and TB7.7 were available as peptide pools while all other classical antigens were recombinant proteins. Ag85A and Ag85B were pooled and tested as a single condition.
DosR regulon encoded antigens
Abilities of DosR antigens to discriminate between TB disease and no TB.
TB cases
0.0 (0.0-140.9
12.0 (0.0-1049.0)
< 6
83 (19/23)
52 (11/21)
< 6.1
83 (19/23)
70 (14/20)
< 0.5
83 (19/23)
76 (16/21)
< 0.1
83 (19/23)
70 (14/20)
< 4.6
87 (20/23)
50 (10/20)
< 9.4
96 (22/23)
50 (10/20)
< 1.1
91 (21/23)
45 (9/20)
< 1.0
91 (21/23)
55 (11/20)
< 2.3
96 (22/23)
45 (9/20)
< 4.9
100 (23/23)
35 (7/20)
0.0 (0.0-2738.0)
12.3 (0.0-1030.0)
< 1.0
83 (19/23)
80 (16/20)
0.0 (0.0-1720.0)
3.2 (0.0-331.6)
< 1.3
91 (21/23)
55 (11/20)
0.0 (0.0-1071)
0.0 (0.0-454.8)
< 1.3
96 (22/23)
45 (9/20)
0.0 (0.0-3456.0)
< 0.1
91 (21/23)
55 (11/20)
TB reactivation antigens
A total of 23 TB reactivation associated antigens (Additional file 3: Table S3) were evaluated in this study. All antigens were available as recombinant proteins. Recognition of most of these antigens was poor in both TB patients and HHCs (data not shown). Two of the most frequently recognized of these antigens (Rv1131 and Rv1471) discriminated between the TB cases and HHCs with p values < 0.05. When the data was assessed by ROC analysis, however, only Rv1131 discriminated between the TB cases and HHCs with an AUC ≥ 0.70 (Additional file 8: Table S8, Additional file 9: Figure S1).
Resuscitation promoting factors (rpfs)
Abilities of resuscitation promoting factors (rpfs) to discriminate between TB disease and no TB.
TB cases
52.2 (0.0-2173.3)
< 0.001
< 1.3
78 (18/23)
85 (17/20)
25.8 (0.0-1056.0)
< 0.9
78 (18/23)
80 (16/20)
29.2 (0.0-1123.5)
< 10.3
74 (17/23)
80 (16/20)
27.2 (0.0-1875.0)
< 0.3
78 (13/23)
80 (16/20)
4.0 (0.0-481.1)
< 1.3
87 (20/23)
60 (12/20)
Starvation antigens and other stress induced proteins
Twenty-four other recombinant antigens, most of which are associated with stress conditions [22] (Additional file 5: Table S5) and 7 starvation induced antigens, all peptide pools (Additional file 6: Table S6), were evaluated in this study. Recognition of these antigens was poor in both TB cases and HHCs. There was no significant difference in the IFN-γ levels elicited by any of the antigens between the TB cases and HHCs (range of p-values, 0.21-0.94). The antigen with the highest AUC for differentiating between the two groups after ROC analysis was Rv0244 (AUC = 0.61). The data indicating the diagnostic potential of these and all the other antigens evaluated in the study is shown in Additional file 8: Table S8 and the ROC curves are shown in (Additional file 9: Figure S1).
Ability of combinations of antigens to discriminate between TB disease and no TB
Validation of ELISA results with the Quantiferon TB Gold ELISA kit
The standard curve for the ELISA employed in this study ranged from 31 pg/ml to 4000 pg/ml. Although the standard curve was useful at detecting high magnitude IFN-γ responses, IFN-γ responses below 31 pg/ml could not be reliably estimated. As optimal cut-off values obtained for the most promising antigens evaluated in this study (after background correction) were as low as 0.5 pg/ml, we performed validation of the results with another ELISA (the commercially available QFT ELISA kit). Supernatants from the best discriminatory antigens (the top five single DosR antigens (Rv2032c, Rv2625c, Rv1996, Rv0081, Rv2624c) and the top three rpfs (Rv0867c, Rv1009 and Rv2389c)) were re-evaluated. This was done in 15 TB cases and 15 HHCs who were randomly selected from our sample bank. Unstimulated control and ESAT-6/CFP-10fp stimulated supernatants from these 30 subjects were also evaluated.
Abilities of antigens to differentiate between TB disease and no TB disease after re-evaluation with the validation ELISA.
TB cases
Cut-off Value
1.0 (0-43.8)
25.5 (0-257.5)
> 29.3
47 (7/15
93 (14/15)
0.6 (0-27.1)
9.8 (0-273.4)
< 1.4
53 (8/15)
87 (13/15)
0.4 (0-29.5)
23.6 (0-297.4)
< 0.1
40 (6/15)
93 (14/15)
0.2 (0-400.0)
1.3 (0-97.1)
< 0.1
20 (3/15)
93 (14/15)
0.8 (0-33.7)
0 (0-195.4)
> 7.6
20 (3/15)
93 (14/15)
0.5 (0-21.0)
1.3 (0-400.0)
< 0.1
47 (7/15)
86 (12/14)
0 (0-3.7)
0 (0-1.7)
< 0.1
27 (4/15)
93 (14/15)
0.3 (0-31.4)
1.3 (0-400.0)
< 0.1
47 (7/15)
87 (13/15)
305 (0-400.0)
308 (0-400.0)
> 441.2
33 (5/15)
96 (26/28)
Accuracy of antigens in diagnosing TB disease when used in combinations.
Resubstitution Classification Matrix
Leave-one-out Cross validation
Wilks lambda
% TB cases
% HHCs
Total %
% TB cases
% HHCs
Rv2624c Rv2389c
Rv2624c Rv0867c
Rv2624c Rv1009
66.7 (10/15)
66.7 (10/15)
Rv2624c Rv0867c
80.0 (12/15)
78.6 (11/14)
80.0 (12/15)
71.4 (10/14)
< 0.0001
86.7 (13/15)
78.6 (11/15)
86.7 (13/15)
< 0.0001
86.7 (13/15)
71.4 (10/14)
< 0.0001
Rv2032 Rv2389c
80.0 (12/15)
Rv2032 Rv0867c
Rv2032 Rv1009
73.3 (11/15)
71.4 (10/14)
Rv2032 Rv2624c
64.3 (9/14)
The diagnostic potential of 118 M.tb infection phase-dependent antigens was investigated in this study. Rpfs were the most discriminatory antigens with combinations of antigens correctly predicting up to 73% of the TB cases and up to 80% of HHCs after cross-validation.
The classical M.tb antigens, evaluated here as 'control antigens', have been extensively studied. Most of these antigens are strongly recognized with high IFN-γ production in TB patients or infected individuals [23–28] and are key components of candidate TB vaccines [29–39] or form part of antigen cocktails that are used in diagnostic tests. The frequent recognition of ESAT-6/CFP-10fp (and ESAT-6 alone) in both TB cases and HHCs, justifies the use of these antigens in all commercially available IGRAs. Recognition of TB7.7 (used in the QFT In Tube test, Cellestis, Australia), Ag85A/B and HSP65 was poor. This is in agreement with earlier studies, which suggest that the majority of response to M.tb infection is largely driven by ESAT-6 and CFP-10, with TB7.7 providing only a small extra benefit (author's unpublished data). When previously evaluated in serodiagnostic approaches, Ag 85A and B also performed poorly [40] while detection of antibodies or antigens to HSP65 in serum and CSF, respectively, diagnosed active TB with an accuracy above 80% [41, 42]. The poor recognition of Ag85A and B, TB7.7 and HSP65 as assessed by IFN-γ production in our study group may suggest that the conditions under which the antigens were tested was not optimal, or perhaps that the humoral and cell mediated responses to these antigens are different. It may also imply that the worth of testing candidate vaccines based on these antigens needs to be reassessed in certain populations. However, it has been shown that responses to TB antigens could be enhanced if antigens are delivered using vectors such as the Bordetella pertusis adenylate cyclase vector [43], use of other adjuvants [32] or the addition of IL-7 [44] and IL-12 [45] into cultures. It is not known if addition of cytokines might have improved upon the diagnostic ability of the antigens. Whether some of these antigens would perform better if used in serological assays [41, 42] requires further investigation. However, the World Health Organization has recently cautioned against the use of serological tests for the diagnosis of TB disease [46].
The DosR regulon of M.tb is upregulated when M.tb is subjected to conditions that mimic latency including hypoxia, nutrient starvation, low nitric oxide or low pH [10, 19, 47–50]. IFN-γ responses elicited by 14 of the DosR antigens evaluated in this study were significantly higher in HHCs compared to TB cases, and 8 of these antigens (Rv2032, Rv2625c, Rv1996, Rv0081, Rv2624c, Rv2006, Rv2629 and Rv2007c) showed promise as diagnostic candidates after ROC analysis, although this promising accuracy was not confirmed by the validation for the five antigens re-evaluated. The inclusion of some DosR regulon encoded antigens into GDA models that best predicted active TB or no TB disease, along with ESAT-6/CFP-10fp or rpfs, may suggest that these antigens are useful diagnostic candidates and need further evaluation in larger studies. The finding that DosR antigens are more frequently recognized in HHCs (many of whom we would expect to be latently infected and all of whom have at least been exposed to M.tb) has also been observed in other studies [13, 19–21]. Recognition of the DosR antigen Rv2628 was associated with cured tuberculosis and remote infection in a study in Italy [51]. Moreover, an increased frequency of the response to Rv2628 at the site of TB disease in patients with active TB has been found [52].
Like the DosR antigens, the reactivation antigens and the rpfs were more frequently recognized in HHCs, with the rpfs being the most discriminatory between the TB and non-TB cases. Rpfs are growth-promoting proteins and have been shown to resuscitate dormant bacteria, as well as enhance the growth of bacteria, including M.tb in both liquid and solid media [53]. M.tb rpfs have been shown to be immunogenic in TST-positive individuals and to elicit strong CD4 and CD8 T cell-dependent responses in vitro, in long-term latently infected individuals [21, 54]. The more frequent recognition of rpfs (believed to be predominantly expressed during the exponential growth phases [53, 55]), in latently infected individuals is consistent with the notion that M.tb exists in a dormant, non-replicating or only slowly replicating state in LTBI [56, 57]. As has been suggested previously, the bacteria may indeed still be replicating but are controlled by the host immune response in an 'active infection' [58]. As suggested by Commandeur et al. [54], the presence of some of the rpfs in culture filtrate may imply higher availability and recognition by immune cells. Furthermore, the existence of M.tb in different metabolic states in its host during infection [57] would imply that T cells are exposed (although perhaps in different amounts) to antigens from different infection phases in vivo-hence their recognition in in vitro stimulation assays. This would also explain the recognition of DosR antigens in TB patients. Whatever the case, antigens that are recognized in both TB patients and latently infected individuals are less well suited for discriminating between different M.tb infection states but could add to the currently used RD1 antigens in the diagnosis of M.tb infection provided they are potent cytokine inducers in short-term culture assays.
To the best of our knowledge, no other study has investigated such a large number of different M.tb infection phase-dependent antigens as diagnostic candidates in a high TB-endemic setting; and little or no information is currently available about the diagnostic potential of most of the antigens investigated in this study. More studies are therefore needed in different population groups to verify the findings of this first screening study. A serious concern in the possible use of new antigens such as those investigated in this study for diagnostic purposes is a lack of specificity for M.tb. Some of the DosR antigens evaluated in this study have been shown to be expressed in BCG vaccine strains [47] but BCG vaccination was reported not to induce T cell responses to DosR antigens, likely because BCG fails to establish long-lived latent infections and therefore may not express (or under express) these antigens in vivo following vaccination [59].
Although none of the classical TB antigens were capable of discriminating between active TB and no TB, ESAT-6/CFP-10fp was included in most of the top GDA models that best discriminated between the presence and absence of TB disease. It is known that the measurement of IFN-γ elicited by ESAT-6/CFP-10 does not discriminate between active TB and LTBI. However, it has proven to be an excellent marker of M.tb infection and this is consistent with the inclusion of ESAT-6/CFP-10fp into all the best discriminatory models. The results suggest that evaluating the DosR antigens or rpfs, which were most predominantly recognized in HHCs, in combination with ESAT-6/CFP-10 could enhance our ability to differentiate LTBI from TB disease in RD1 antigen-positive individuals. When IFN-γ responses against the different antigens were analysed only amongst participants that responded to ESAT-6/CFP-10fp, significant p-values were obtained for all the five rpfs (Rv0867c, Rv2389c, Rv2450c, Rv1009, Rv1884c), 11 DosR encoded antigens (Rv3129, Rv2625c, Rv1996, Rv2032, Rv3126c, Rv2631, Rv3130c, Rv2624c, Rv2007c, Rv3131, Rv3127) and two TB reactivation antigens (Rv1471, Rv3862c). Furthermore, the AUCs for all these 18 antigens in discriminating between TB disease and no TB in the ESAT-6/CFP-10fp responsive participants was above 0.70 (data not shown). Because of the explorative nature of this study, the contributions of the different antigens in the predictive models will need to be investigated further in ongoing follow-up studies.
The main limitations of our study include the relatively small sample size, the use of 7-day WBA instead of overnight assays which would be more suitable for a diagnostic study, and the unavailability of accurate LTBI diagnostic data for the HHCs. The HHCs that participated in this study were recruited from a high TB endemic area [3, 60] where it is known that up to 89% of HHCs may be TST positive, with 74% being QFT positive in a previous study [5, 13, 17]. However the M.tb infection status of participants recruited into future follow up studies should be better characterized, so as to enable a more accurate estimation of the discriminative abilities of the antigens between active TB disease and LTBI. This could be done by means of IGRAs and appropriate contact scores based on TB exposure gradient as has been done previously [5, 6, 61]. For the majority of the antigens evaluated in this study, no information was previously available about their immunogenicity in M.tb infected individuals. We therefore chose to evaluate the antigens using a long-term whole blood culture assay in order to detect any existing immune responses to the antigens, including memory responses. Future evaluation of diagnostic candidates should be done in larger numbers of participants, in overnight assays to detect effector cell responses, and preferably using a prospective study design. Potentially useful candidates should also be evaluated in children, immunocompromised individuals, extrapulmonary TB cases and also in individuals with other lung diseases. Because of the need for new TB diagnostic tests to be rapid and less technically demanding, the use of other platforms such as serodiagnosis and the possibility of employing cocktails of antigens should be evaluated. Our data indicates that the two ELISAs employed in this study might not deliver comparable results as only three of the eight promising antigens re-evaluated with the QFT ELISA showed the same promising accuracy obtained with the "BD ELISA". The reasons behind this discrepancy were not investigated further in this study as these technical issues are beyond the scope of this screening study that was designed to identify possible diagnostic antigen candidates. The discrepancies could however, be due to technical aspects that might be inherent in the two ELISAs (the "BD ELISA" with an 8-point 4PL standard curve ranging from 31 pg/ml to 4000 pg/ml versus the QFT ELISA with a 3-point linear standard curve ranging from 0.25 IU/ml to 4.0 IU/ml). ELISA assays used in future studies should be carefully selected, taking into consideration technical aspects including detection limits, to enable more accurate detection of a broad range of IFN-γ responses. Finally, multiplex cytokine analysis assays could be used to evaluate other biomarkers [1, 17, 62] in supernatants from antigens that did or did not elicit IFN-γ responses since the lack of an IFN-γ response does not necessarily imply that the antigen is not recognized by T cells. The possibility of establishing a useful diagnostic signature comprising a pattern of host responses to different M.tb antigens should be investigated.
In conclusion, IFN-γ responses to TB rpfs associate with latency and show promise as TB diagnostic candidates. The findings of this study are preliminary and require validation in other studies and in other settings.
We are grateful to Professor Martin Kidd of the Centre for Statistical Consultation of the University of Stellenbosch for assistance with the analysis of the data. This work received financial support from the Bill & Melinda Gates Foundation Grand Challenge 6 (BMGFGC6, grant no 37772), Principal Investigator SHE Kaufmann.
Authors' Affiliations
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Pre-publication history
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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Light yet filled with love: floral arrangements for Advent
With Christmas right around the corner many people have already started making traditional wreaths and candles for Advent. The lights will lead us to Christmas, the holiday of togetherness and during which traditional decorations, Yuletide greenery and floral arrangements are present everywhere. This creative arrangement is sure to trigger plenty of new ideas!
At the dinner table, at a party or simply together: we celebrate the end of the year in the company of others as much as we can; or by thinking of them. The warmth exuded by a traditional Advent wreath is of inestimable value. This combination of vigorous Yuletide green and strong Rhodos roses give this arrangement a highly a festive note. With a beautiful ribbon that brings everything – and everyone – together.
In this busy time of year you deserve a gift. This is why you can make use of these beautiful images (HR) at no cost via this link.
The ribbon unifies all elements!

subset: commoncrawl


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Josef Herman was born into a poor Jewish working-class family in Warsaw in 1911. He worked as an apprentice typesetter and graphic artist before briefly training at the Warsaw School of Art (1930–32), establishing a life-long interest in portraying working people. He co-founded the left-wing artistic group 'the Phrygian Bonnet' in 1934. In 1938 amid rising anti-Semitism Herman fled to Brussels (1938–40), then following the German invasion of Belgium in May 1940, he fled again through France and England, settling in Glasgow (1940–43). There, together with Jankel Adler and sculptor Benno Schotz, he contributed to a remarkable artistic renaissance spearheaded by the Scottish colourist J. D. Fergusson.In October 1941 Herman held his first UK exhibition in Glasgow; reprised in Edinburgh in 1942. In the same year he learned through the Red Cross that his entire family had perished in the Warsaw Ghetto. He had already begun the powerful, nostalgic body of work on Jewish themes, the Memory of Memories series, sketched quickly and fluidly from memory or imagination and this now darkened to include works referencing pogroms and the destruction of the Ghetto. In 1943 Herman moved to London, holding his first London exhibition (Reid and Lefevre Gallery) with the then little-known L. S. Lowry, and the Memory of Memories series concluded.
Refugees is a rare, important early painting, thought lost for over 60 years. Herman destroyed the majority of work from this period in 1948, considering it too influenced by Chagall. Blue was the dominant colour of Herman's Glasgow years, used as a nostalgic evocation of a lost Warsaw with its moonlit spires. Like much of Herman's Glasgow work, this painting draws strongly on his eastern European Jewish heritage and themes. However the refugees also represent the wider displacement of peoples uprooted and forced into exile by the upheavals of the Second World War. The family's unknown fate is symbolized by the cat with a mouse dangling from its jaw. The treatment of the figures reflects Herman's admiration for Käthe Kollwitz, while the fearful child with her hand in her mouth is reminiscent of Goya.
Ben Uri holds eight works by Herman including the early pen-and-ink sketch Musicians (c.1940–43) and a portrait drawing of the Yiddish poet, Avram Stencl. In 2011 it mounted the largest exhibition to date of Herman's work from this rare period.
During the summer of 1944, on a chance visit to the Welsh mining village of Ystradgynlais Herman experienced an artistic epiphany and made his home among this close-knit, hard-working community for the next 11 years, establishing his reputation with dignified and empathetic portrayals of miners, which remain his best-known works. He held numerous solo and joint exhibitions, including one at Ben Uri with fellow émigré painter, Martin Bloch, in 1949 and another with Lowry and Nehemiah Azaz (Wakefield City Art Gallery, 1955) and retrospectives in London (1956; 1980) and Glasgow (1975). Awarded the OBE in 1981, he was elected a Royal Academician in 1990. Ben Uri holds 10 works by Herman in the Collection.


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No one can not like hot chocolate. I like mine with dark chocolate and flavoured with cinnamon and orange. And this one is no ordinary "milk with sugar and cocoa" hot chocolate. This is milk with some cream that is infused with cinnamon and orange zest, heated and then poured over some chopped chocolate. The hot, flavoured milk will melt the chocolate and result in the most delicious, thick hot chocolate that just keeps getting thicker and more chocolaty as it cools.
Depending on your taste, substitute the dark chocolate with milk chocolate if you want it sweeter and play around with milk-cream ratio to get the desired consistency.
I leave with you some of my favourite cookbooks that have enthralled and inspired me ever since I've started writing this blog. Some have taught me, some have appealed to my fuss-free nature, some have taught me to work with fresh and seasonal produce and some have simply spoken a language I could connect with.
A dear friend recently told me, "The best is yet to come..". With that beautiful sentiment in mind, I wish you and yours, all the best that life has to offer in 2014!! Happy New Year!!
Dark Hot Chocolate
Serves one.
- 150 mls milk
- 2 tablespoon cream
- 50 gms dark chocolate, roughly chopped
- 1/2 cinnamon stick
- zest of one orange
- splash of rum/coffee liqueur (optional)
- Place the chopped chocolate in a mug.
- Put the milk, cream, cinnamon and orange zest in a saucepan. Heat it on a medium flame and take it off the heat, just before it is going to boil.
- Strain the milk mixture through a sieve onto the chocolate in the mug.
- Keep stirring till the chocolate melts.
- Add a splash of rum/coffee liqueur, if you like. Serve.


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Beat The Clock! Aging Tips To Turn Back Time
Many people, especially women, have a tough time with aging. But there are a few simple ways that you can postpone the aging process and manage to look and feel young for many years to come. Below are a few tips that have been accumulated to give you an advantage over the aging process.
Switch away from real dairy to dairy substitutes like soy or almond milk. There have been quite a few studies linking dairy products with aging skin. If you want to avoid wrinkles as you age, put down the dairy. The substitutes that are on the market are healthy and tasty so give them a shot.
Increasing your social activities can improve your lifestyle as you get older. Being part of a group can help you to keep learning and experiencing new things. Join a seniors group, a craft class, or a cooking class. Keeping busy will give you no time to feel older!
Resveratrol can be beneficial. There have been promising studies done on this compound. Resveratrol is a natural antioxidant found in grapes and nuts, that flushes your digestive system when taken regularly. A good source of Resveratol is in Polygonum cuspidatum or Fallopia japonica, this is where they get it for supplements. Another place to find it is the South American shrub called Senna quinquangulata.
In order to look young and slow down the aging process, it is necessary that you eat good amounts of fruits, daily. Like vegetables, fruits contain antioxidants that help your body with hydration. Another thing that fruits have is vitamin C, which helps you to maintain very radiant looking skin.
Even if your body is deteriorating, you do not have to let your spirit deteriorate as well. Keep growing as a person through reading books, sharing stories with loved ones or enjoying a good old movie now and then. Keep your youthful spirit alive as long as you live.
As you age, discuss with your doctor what vitamins and supplements you want to take. Often times our bodies become less efficient at extracting the nutrients we need from the food eat, so we need supplements. Ensuring you get the right nutrition is of paramount importance as you go through the aging process.
Make sure you're only drinking alcohol in moderation. For those under 65, this means you shouldn't drink more than two glasses a day. If you're over 65, this means you shouldn't drink more than one glass a day. If you're going to drink alcohol try drinking wine instead since it's shown to benefit health in small doses, unlike beer or hard liqueur.
Staying properly hydrated has never been more important to you than now! Aging is hard on the body and providing it with plenty of water will help flush toxins, bring nutrients to cells, hydrate skin and make it easier on every function of your body! Try this. Most experts recommend about eight glasses of water each day, so drink up for healthier aging!
As you get age, so does your brain. Studies have shown that exercising your brain is as important as exercising your body. Memory exercises will improve the mind and help stave off memory illness or dementia. Small exercises like memorizing 10 objects as you take a walk through your neighborhood, then writing them down when you get home is a good example to the mind nimble and alert.
Keep your mind active. "Use it or lose it" is one phrase that is true. Whether you do logic puzzles or learn a new language, keeping your brain working is an essential ingredient to life as an older person. Keep your mind occupied and it will keep working well for you.
While an occasional drink every now and then is perfectly acceptable, in order to slow the aging process, alcohol is something that should be avoided. In excess, alcohol can cause cardiovascular diseases, certain cancers, can weaken your immune system and affect your system of balance resulting in injuries. By limiting alcohol, you are helping your body fight the inevitable aging process.
A key to aging well is to maintain a good relationship with your physician. By getting yearly preventative checkups as well as any checkups that are necessary in between, you are taking a proactive approach to aging. There are many diseases that when caught early are highly treatable. Early disease treatment will definitely slow down your aging process.
Don't overeat! Overeating is one of the most common factors in shortening your life span. You don't want to starve yourself, but you should be conscious of the amount of calories you're taking in each day. Check with your doctor and find out the amount of calories you should be taking in based on your age, gender, and body type, and try to stick to that number.
There is no magic pill to reverse aging. There is no snake water magic potion for a youthful appearance. Making healthy changes to your lifestyle and diet can give you a zestful approach to living. Remember that issues due to aging takes a lifetime to develop so it will not be reversed overnight when you start giving your body what it needs.
The older you get the more difficult it will become for you to find and maintain a job. This is for two reasons, first there is a general fear of hiring people who are elderly, but secondly it will actually become more difficult for you to maintain the same level of energy you need for the jobs. So, it is important to stay fit, and to keep up to date with changes in your area of interest or expertise.
If you are going to be going out in the summer, make sure to apply a coat of sunscreen to your face and neck. The sun can have damaging affects if you are exposed for a long time and can lead to leathery skin in the future. Apply a coat of sunscreen to slow down the aging process.
Aging is a natural part of life, but that doesn't mean you have to look and feel horrible. These tips will give you a bit of an advantage to keep your body looking and feeling fit for many more years. Hopefully you've learned a few new tricks from this article. Good luck with your battle against time.


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Project Description
No flower lifts the spirits quite like a sunflower can. Bright and cheery, sunflowers originated in the Americas in 1000 B.C. The sunflower's petals have been likened to the bright yellow rays of sunshine, which evoke feelings of warmth and happiness in our collective consciousness. In addition, the sunflower is often associated with adoration and longevity. Taking all these facts into consideration, what better motif for an occasion celebrating the anniversary of a significant person's birth? Three muted green tiers, each edged with a braid of interwoven ribbons, form the backdrop for this plethora of large sunflowers that bring a golden glow to this work. Each sunflower is a reminder of the sun, itself, and "Sunflowers Galore" hints of promises of good things to come.


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October 15, 2008
Sol Food
3 comments:
Looks so relaxing.ReplyDelete
I love your pics over at bloesem!
I know a great tip for getting the stains out of your great-grands lovely pitcher. Soak it in hydrogen peroxide. It's non toxic and wont damage the piece at all. Crazing will remain beautiful and those stains would be all gone!
(Heavy staining may need to be soaked for a week or more)
Wow that place looks amazing! I also loved your pictures on bloesem too!ReplyDelete
Hi Claire! It was relaxing and that was without getting a massage (lots of folks wandering about with their white robes on!). THANKS for the tip! That is GREAT to know! Though truthfully I kinda like the staining a bit. But I can be fickle...so this could come in handy yet!ReplyDelete
please sir...It was indeed delightful! Thanks for the compliment!
Thanks for the comments! :)
Thank you so much for taking the time to comment. I always appreciate your thoughts. Your comment will appear as soon as I can publish it.
p.s. - Contrary opinions or constructive criticism are also fine but "The Bedlam" doesnt' serve as a platform for random (or anonymous) acts of offensiveness. Rude? Deleted.


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CEC/CEU Update: Can Fit Pro has just approved NPI's Online Certified Posture Specialist Program for 3.0 PTS AND NPI's Onsite Posture Analysis and Correction workshop for 4.0 PTS!
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Just learning about molecular hydrogen? Perhaps these questions are yours also. Read and discover more about this miracle molecule.
6 Important Questions About Molecular Hydrogen
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Find accommodations in Bray-et-Lû with the hotel list provided below. Search for cheap and discounted hotel and motel rates in or near Bray-et-Lû, France for your personal leisure or group travel. We show the best Bray-et-Lû hotel rooms. Review the Bray-et-Lû hotel list below to find the perfect lodging. We also have a map of the Bray-et-Lû hotels. Planning a group? Lock in Bray-et-Lû Group Hotel Discounts
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Viral hepatitis kills 1.5 million people worldwide each year.
That's as many people as HIV / AIDS.
Transmission: Hepatitis A is spread mainly through eating food or drinking water that has been contaminated by the faeces of an infected person. It can also be spread by eating raw shellfish that have come from water contaminated by sewage.
Prevention: There is a vaccination for hepatitis A. Treatment within a few weeks of exposure to the virus can also bring short term immunity. You can reduce the risk of exposure by practicing good hygiene and sanitation, and avoiding drinking water that has come from a potentially unsafe source.
Treatment: As hepatitis A only causes acute hepatitis, the body is often able to clear the infection itself within a few weeks. However, hepatitis A infections can sometimes cause further complications.
Transmission: Hepatitis B is transmitted through contact with the blood or other body fluids (i.e. saliva, semen and vaginal fluid) of an infected person. It can be passed on from mother to child during childbirth.
Prevention: There is a vaccination that can prevent infection. If you have not been vaccinated, to reduce chances of exposure it is best to use condoms, and to avoid sharing needles or items such as toothbrushes, razors or nail scissors with an infected person. It is also wise to avoid getting tattoos or body piercings from unlicensed facilities.
Treatment: Drugs such as alpha interferon and peginterferon and a variety of antiviral drugs are available which slow the replication of the virus and occasionally result in its clearance. Children born to mothers infected with hepatitis B should also be vaccinated within 12 hours of birth, as this can prevent an infection that will most likely progress to chronic hepatitis B.
Transmission: Hepatitis C is mainly spread through blood-to-blood contact. In rare cases it can be transmitted through certain sexual practises and during childbirth.
Prevention: There is no vaccination for hepatitis C. It is therefore necessary to reduce risk of exposure, by avoiding sharing needles and other items such as toothbrushes, razors or nail scissors with an infected person. It is also wise to avoid getting tattoos or body piercings from unlicensed facilities.
Treatment: Treatment for chronic hepatitis C aims to eradicate the virus. It often involves a combination of pegylated interferon and ribavirin, and there is increasing use of potent direct acting antiviral drugs, with and without interferon. People with different genotypes respond differently to treatment, some more successfully than others
If you would like more information on Hepatitis please see: http://www.worldhepatitisday.info/en/about-hepatitis
Vaccine is available at the heath department for Hepatitis A & B. Call 304-623-9308 for more information.


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491. 3-3/4" tall
492. Close-up/partial shot of something that everyone has seen before.
493. 9" x 2" x 2.5"
Someone sent this one in looking to find out what it is.
Fully assembled:
Shown removed in this photo, the round part isn't a tight fit into the case. You can see some felt cushions that hold it in. The inside of the rectangular case is unfinished and has no odor or noticeable stains.
The round piece comes apart. It's lined with brass and had some very fine grained, dried out green sponge or foam inside. You can see there are three holes that extend into the brass lining.
494. 2-3/4" long
495. 7-1/4" long


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I would like to thank letter writer Lois Knight for letting us know what happened to the man selling produce on Camp Drive. We had wondered why he closed so suddenly.
We are retired and on a fixed income and it was very convenient for us to stop by on our way to or from the shopping areas instead of driving miles to find fresh produce. We also enjoyed visiting while buying produce.
in town need
to be reset
Something special happened on April 15: Tens of thousands of South Carolinians from all walks of life assembled for "TEA parties" at dozens of locations across the state. Their rallies, of course, came on a day many people have come to dread – Tax Day.
Ken Hudson has distinguished himself in a host of endeavors in a life of service to others. Hudson had an outstanding career in education working with the Lancaster County School District.
The plus for the district is that Hudson was able to share his talent with schools throughout the county. He worked in a variety of fields, including guidance, teaching, coaching, administration and as an athletics director.
Vegetable gardens were once commonplace in Lancaster County. So, when springtime rolled around, it was time to prepare the garden.
Time to plow the ground, fertilize the soil and plant the seeds for what would hopefully be a bountiful summer crop. Green beans, limas, peas, okra, squash, cucumbers, tomatoes and corn. Yum, how tasty they were when they were fresh from the garden in the good ole summertime.
Letters to the editor
Red Rose Trivia Trek
was a success
There is more to the story of CareNet and more people to thank than were listed in the March 25 article, "CareNet helping people every day."
I had the honor and priviledge to work with Dr. Malcolm Edwards, Dr. Jim Holt and Dr. John Story in 1991 to start CareNet.
Several years ago Lancaster City Council voted to implement a hospitality tax in the city of Lancaster. The hospitality tax is a 2 percent tax levied on all food, beverage and alcohol sales in bars, restaurants and other establishments in the city limits. The money is to be used to promote local tourism.
Copyright © 2019
The Lancaster News is your source for local news, sports, events, and information in Lancaster County and Lancaster, South Carolina, and the surrounding area..


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O-Ring Assortment, Buna N, 70 Shore A SAE, Number of Pieces: 200, Number of Sizes: 12
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By Steve Wickham
Thus says the LORD: Stand at the crossroads, and look, and ask for the ancient paths, where the good way lies; and walk in it, and find rest for your souls.
~Jeremiah 6:16a-c (NRSV)
Whoever would be indwelt by the Spirit must judge their life for any hidden iniquities.
~A.W. Tozer (modified for gender inclusivity))
The Holy Spirit – the Lord of true spirituality – is no coercer of souls. Though all the power in the universe is spoken forth by the Spirit, there is nothing gentler. And this Spirit is grieved far easier than any of us think.
Sharpening our spiritual game is as simple or hard as understanding, discerning, and obeying the gentle trickle of spiritual communication that can only be distinguished by a soul palpably surrendered in that moment.
We know by the way our consciences function, the moment's guilt for those hidden things hidden from others but never from God, and how grieved we are (let alone the Holy Spirit) at such folly; we are deceived daily and only a surrendered heart can, again and again, save us.
The true spiritual life is an existence poised at the crossroads, not in indecision but for the spiritual rationale to ask, to seek, and to knock (Matthew 7:7).
The crossroad is spiritual position 'A', because it resolves to stay on the ancient path; one that, in terms of time and space, is so dynamic, the path is lost the moment we go alone. This crossroad is the spiritual reality of life; it situates itself in our present moments, as we walk along in our spiritual walk, because at any time, usually through the rising of the flesh, or complacency, fatigue or frustration, we turn to the left or right and away from the crossroad we go.
Life with God is life, constantly as it rests in the body, at the crossroads.
Sharpening our spiritual game is understanding life at the crossroad – with sight of both Spirit and flesh at our beckoning – is the cherished Presence of the Lord.
There, and there alone, with no desire and no thought for worldliness, the Spirit makes its home; our spiritual game, for that moment, is sharp.
The truly spiritual person is mature enough to understand that spiritual vitality depends comprehensively on the ability to allow God to search them – "for any hidden iniquities."
Repentance is central to spiritual sharpness; as left is to right, and north is to south, because we are sinful creatures, there is penitence required – the heart put right – for fellowship before God; and there is no spirituality without the Lord.
Judging our lives and confessing our sin is, and will always be, the absolute centre of spiritual sharpness.
The beauty of spirituality is the love of choice. God is both all-powerful and incomprehensibly gentle. Becoming spiritually sharp is a choice; only basic acts are required – yet, these are not easy, for we necessarily must swallow our pride.
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ISRN Thermodynamics
Volume 2012, Article ID 204104, 3 pages
The Born Formula Describes Enthalpy of Ions Solvation
Institute of Chemical Kinetics and Combustion, Novosibirsk State University, Novosibirsk 630090, Russia
Received 3 February 2012; Accepted 26 February 2012
Academic Editor: M. Manciu
Copyright © 2012 Nikolai Bazhin. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The process of ion solvation has been studied in the reversible system using the Van't Hoff equilibrium box. It is shown that the Born formula for solvation energy describes a change in enthalpy rather than in Gibbs energy.
1. Introduction
Solvation energy is usually taken as the difference in work which results from ion charging in both vacuum and liquid phase due to a mental process [1]. For an approximate, simple estimate of solvation energy, one can use the Born formula [1] according to which the solvation energy () is the difference in the energy of charging the sphere of radius to charge in both vacuum and medium with a dielectric constant where is an electric constant, and is the Avogadro number. According to Born, (1) is the work obtained by transferring a charged sphere from vacuum to condensed medium. The work manifests itself in solvation heat [1]. Since the system temperature is constant, the heat emitted passes to a thermostat. It is assumed then that Born has taken solvation energy as the change in either internal energy or enthalpy upon solvation. However, discussing Born's work, the authors [2] assert that without any doubts, value (1) calculated by Born is the maximum work performed by electric forces during ion dissolving. Therefore, in [2], (1) is equated with the change in the Gibbs energy which allowed the authors [2] to calculate solvation enthalpy as Equation (1) fails to quantitatively describe ion solvation in numerical form. The advantage is that it can be used to qualitatively estimate the dependence of solvation energy on ion size, medium's dielectric constant, and temperature. It is of importance then to ascertain whether (1) is the Gibbs function or the solvation enthalpy.
We will omit here the problems of the applicability of (1), considered, for example, in [3–10].
Since the energy of charging is the work, formula (1) is commonly accepted as the change in the Gibbs function upon solvation which causes, however, some doubts for the following reasons.(1)To calculate the change in the Gibbs function, one should accurately determine the initial and final states of the system. To derive formula (1), the charging of only one particle is considered, and the result obtained is multiplied by the Avogadro number to calculate the charging energy per one mole. As compared with enthalpy, in the initial state, the Gibbs function is pressure dependent, and, in the final state, it depends on ion concentration. Thus, it is impossible to describe the change in the Gibbs function in terms of (1).(2)There is no evidence that formula (1) is sure to describe the change in the Gibbs function rather than the change in other values, for example, in enthalpy.
The goal of the present work is to solve this problem by means of the Van't Hoff equilibrium box (VHEB) proposed by Van't Hoff to derive an equilibrium constant. To this end, the manuals on chemical thermodynamics [11, 12] consider the VHEB as an old alternative of the method of chemical potentials. At present, the VHEB is very useful to solve qualitative problems. Thus, for example, in [13], the VHEB was used to demonstrate that the reversible work at in the systems, including chemical reactions, arises only due to the thermal energy of the environment, and the energy evolved by reactions is not employed to produce useful work.
2. Solvation
The change in the Gibbs function between two states of the system is independent of the type of transition between these states. This transition can be either reversible or irreversible. However, to calculate the change in the Gibbs function, the transition should be reversible because, in this case, the calculation of the change in the Gibbs function becomes more available. The reversible solvation process is performed in this paper by analogy as described in [13] for coal oxidation. The system under study is considered ideal.
Let us describe first the standard initial and the final states. The final state is the electrolyte solution. Due to Alberty [14], the standard state of an electrolyte solution is "the hypothetically ideal solution at unit activity in which ions have the properties they do at infinite dilution." We assume then that a standard state of ions in gas is a hypothetical gas at 1 bar, in which the ions have the properties they do at infinite expansion. Thus, in these hypothetical standard states, the electrostatic interaction of ions is cut off which alleviates the calculation of thermodynamic values, describing the process of solvation.
Consider now the solvation process. Gaseous ions are assumed to occupy a very large volume. In addition, the volume of the liquid-phase system is also assumed very large. The system is located in a thermostat. Let us reversibly convert the part of the gaseous system from the initial state into the final one. We calculate the change in the thermodynamic functions upon transition of a hypothetical system from the standard state in the gas phase to that in the liquid state in the course of a conceptual process, consisting of two stages.
Step 1. At step 1 we take 1 mole of ions in the gaseous state at bar and expand the ion gas reversible to pressure , at which the chemical potential of ions in gas becomes equal to that in solution. The reversible process is accompanied obligatory by useful work production , and the change in the Gibbs function of the ions is equal to The change in enthalpy of ideal ion gas expansion is of the form The value of is unknown. Value (3) cannot be given in terms of system parameters in the framework of the approach used. Upon expansion, the reversible work is performed which can be converted into the potential energy of the load. The work is performed only by the thermal thermostat energy because, in the system, there are no other energy sources. Thus, the change in the thermostat enthalpy during gas expansion at the first step is
Step 2. At the final pressure , we slowly introduce ions from the gas phase to solution through, for example, a semipermeable membrane. In this case, the Gibbs function does not change because of the equality of the chemical potentials of ions in the gas and liquid phases, and, thus,
Hence, the full change in the Gibbs function upon solvation process is equal to useful work of the ion gas expansion during first step
It is worth noting that no relation was established between and formula (1).
The process of solvation results in heat release. The reaction of ion dissolution is similar to that of coal oxidation [13]. The value of the change in the ions enthalpy at the second step is calculated from (1) because, in terms of the law of energy conservation, the difference in work on sphere charging in both vacuum and liquid should convert into another type of energy, represented in our case, by the solvation reaction heat Hence, the full enthalpy of solvation process is calculated via the Born formula (1) The change in the thermostat enthalpy at the second step during gas expansion is The full thermostat enthalpy change in the reversible process is In the case of the irreversible process , the full thermostat enthalpy change is equal to The change in the Gibbs function (7) cannot be equated to the negative value of solvation energy (1) because the change in the Gibbs function in the reversible process determines the value of useful, reversible work rather than of the heat emitted.
Thus, the Born function (1) can be used to calculate only the solvation enthalpy.
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Ever amused the idea 'I could do that myself'?
The question is, is DIY roof repair a smart idea?
I have actually been a plumbing professional for even more than 20 years and also seen a lot of construction jobs, noticed just how home builders do points, exactly how electrical contractors wire up and also how various other tradespersons work. Sometimes I have stated 'I can do that' and also wound up having to obtain a qualified tradesperson to modify or finish the (non plumbing) job I have actually started.
I tried electrical wiring on my shed as soon as, then component way with decided to call the electrician electricians toronto just to be informed he had to remove all I had done and also start once more. I currently realize there is a factor they are certified tradesmen, much like me, or even though I understand plenty, I need to leave that work to them as well as stick to just what I'm learnt.
So exactly what's so tough regarding roof replacement?
I presume it's not that it's hard, merely that it's tough to do it best and also to the laws. You see, ultimately all of it comes down to rules.
Lets state you had a bad tornado eventually and also had water leak into the house as well as cause water damages. You would call the insurance business, they then send out an assessor who examines whats destroyed and also why. If any kind of suspicious locals are discovered they ask who mounted it.
Now, now, if you had an expert do the task as well as there were issues found with the job then either they or their insurance policy deals with it, however if it's discovered that a person unqualified set up the job then you have no guarantee that your insurance coverage will certainly cover the issues.
You might state 'if I installed it there would not be any type of troubles'. Allow me take you with a lot of factors where the regulations and also producer standards reveal there are several other locations to take into consideration than you might believe.
Are there any sort of council limiting factors on just what you can do - heritage overlays, land agreements, council laws, BAL considerations etc?
Certain building laws - is constructing insurance policy needed, does the roofing system structure obey with present laws?
Meteorological information needed when sizing guttering and downpipe sizes as well as locations of roof dimension, and ways to institute overflow defense?
Do the roof battens abide and also distance in between battens, what roof covering profile is needed due to incline limits?
What gutter system overhang is required and also why, how much cover on flashings is needed and also why?
Roof covering seepages - what type of flashing/dektite is to be used and also ways to permit development as well as contraction?
Exist any sort of power wires in wrong locations exposed to mechanical damages or where a person can screw right into?
Fall protection - this is currently an extremely huge concern and needs much consideration, even on your own residence as new OHS regulations hold the property owner liable where there is no contractor involved.
The wind as well as weather considerations when mounting the roofing and the security involved.
There are still more locations to cover when taking a look at installing a roof in a specialist way, yet the biggest factor for using certified tradesmen is understanding that your finished job is covered by a 6 year guarantee, giving you amount to peace of mind.
At the end of the day, your roof covering is one of the first things that is seen and is the crowning glory of your home, so you desire a person that takes satisfaction in doing the most effective task they can.
You see, it's not simply a concern of getting rid of the old sheet and setting up the brand-new, rules transform, council requirements transform, building policies change as well as a lot more. You might reach completion of the work and also have your neighbour complain regarding something as well as if there is a concern you have not covered then you're in for fines and also even having to alter the work.
Then you have the concern of selling the residence, if you do not have your appropriate certificates and/or insurance then you will not obtain it via the particular legal needs that are in area currently.
Currently days there are a lot of mistakes and also locations of feasible litigation it's merely unworthy trying to save money by doing it yourself. If you are ever in question of exactly what you can do a cannot, get in touch with your local council as well as they will certainly provide you direction.
As the supervisor of Fresh Water Plumbing I have the satisfaction of functioning with you the home owner, working via your wants and also needs as well as delivering you a finished product that shows quality craftsmanship.
You the consumer are the most vital part of any task and also the completed item is not just a job of fine art for you, it's also a screen piece showing off our abilities and commitment to top quality.


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