Century-long expansion of hydrating cement counteracting concrete shrinkage due to humidity drop from selfdesiccation or external drying

A physically based model for auotgenous shrinkage and swelling of portland cement paste is necessary for computation of long-time hydgrothermal effects in concrete structures. The goal is to propose such a model. As known since 1887, the volume of cement hydration products is slightly smaller than the original volume of cement and water (chemical shrinkage). Nevertheless, this does not imply that the hydration reaction results in contraction of the concrete and cement paste. According to the authors’ recently proposed paradigm, the opposite is true for the entire lifetime of porous cement paste as a whole. The hydration process causes permanent volume expansion of the porous cement paste as a whole, due to the growth of C–S–H shells around anhydrous cement grains which pushes the neighbors apart, while the volume reduction of hydration products contributes to porosity. Additional expansion can happen due to the growth of ettringite and portlandite crystals. On the material scale, the expansion always dominates over the contraction, i.e., the hydration per se is, in the bulk, always and permanently expansive, while the source of all of the observed shrinkage, both autogenous and drying, is the compressive elastic or viscoelastic strain in the solid skeleton caused by a decrease of chemical potential of pore water, along with the associated decrease in pore relative humidity. As a result, the selfdesiccation, shrinkage and swelling can all be predicted from one and the same unified model, in which, furthermore, the low-density and high-density C–S–H are distinguished. A new thermodynamic formulation of unsaturated poromechanics with capillarity and adsorption is presented. The recently formulated local continuum model for calculating the evolution of hydration degree and a new formulation of nonlinear desorption isotherm are important for realistic and efficient finite element analysis of shrinkage and swelling. Comparisons with the existing relevant experimental evidence validate the proposed model

Century-long expansion of hydrating cement counteracting concrete shrinkage due to humidity drop from selfdesiccation or external drying

A physically based model for auotgenous shrinkage and swelling of portland cement paste is necessary for computation of long-time hydgrothermal effects in concrete structures. The goal is to propose such a model. As known since 1887, the volume of cement hydration products is slightly smaller than the original volume of cement and water (chemical shrinkage). Nevertheless, this does not imply that the hydration reaction results in contraction of the concrete and cement paste. According to the authors’ recently proposed paradigm, the opposite is true for the entire lifetime of porous cement paste as a whole. The hydration process causes permanent volume expansion of the porous cement paste as a whole, due to the growth of C–S–H shells around anhydrous cement grains which pushes the neighbors apart, while the volume reduction of hydration products contributes to porosity. Additional expansion can happen due to the growth of ettringite and portlandite crystals. On the material scale, the expansion always dominates over the contraction, i.e., the hydration per se is, in the bulk, always and permanently expansive, while the source of all of the observed shrinkage, both autogenous and drying, is the compressive elastic or viscoelastic strain in the solid skeleton caused by a decrease of chemical potential of pore water, along with the associated decrease in pore relative humidity. As a result, the selfdesiccation, shrinkage and swelling can all be predicted from one and the same unified model, in which, furthermore, the low-density and high-density C–S–H are distinguished. A new thermodynamic formulation of unsaturated poromechanics with capillarity and adsorption is presented. The recently formulated local continuum model for calculating the evolution of hydration degree and a new formulation of nonlinear desorption isotherm are important for realistic and efficient finite element analysis of shrinkage and swelling. Comparisons with the existing relevant experimental evidence validate the proposed model

Neurobrucellosis: Clinical and laboratory findings in 22 patients

Brucellosis is a multisystem disease with diverse clinical presentations and involvement of the nervous system is considered to 5 to be 10% in adult patients and 1% in children. The presentations of neurobrucellosis includes meningoencephalitis, subarachnoid haemorrhage, myelitis, radiculoneuritis, intracerebral and epidural abscess, psychosis and vascular syndrome. Twenty-two patients with neurobrucellosis are described. Ten patients had meningoencephalitis, seven patients had meningitis, three patients had polyradiculopathy and one patient presented with spinal epidural abscess and one patient had brain abscess. Results of an agglutination test for Brucella in serum were positive for all patients (>1:160); eight of 15 patients had positive agglutination test in CSF. Five patients had positive blood cultures, 3 patients had positive bone marrow cultures and 2 of 15 patients had positive CSF cultures. All of cultures were Brucella Mellitensis. Antimicrobial treatment included concurrent administration of Doxycycline, Rifampin and Trimethoprim-Sulfametoxazole. Four patients received Dexamethason concurrently. In conclusion, nervous system involvement is a serious manifestation of brucellosis. As brucellosis is an endemic disease in Iran we suggest that brucellosis be investigated with neurological symptoms and signs

ERYTHEMA INDURATUM

The clinical and histological feature of 52 years old woman with erythema induratum are discribed The characteristic cutaneous lesions on the legs of middle-aged woman were violaceous, indurated nodules, 1 to 2 cm in diameter which were painful, occasionally ulcerated and could heal with scarring. The diagnosis was confirmed by a strongly positive tuberculin test, histologic feature and by clearing of lesions after antituberculosis therapy. The histologic feature was infiltration of dermis and subcutaneous by inflammatory cells with epithelioid cells and multinucleated giant Langhans cell

Pulmonary Tuberculosis in Patients with HIV/AIDS in Iran

"nBackground: Pulmonary tuberculosis is still the most common form of tuberculosis in HIV infected patients having differ­ent presentations according to the degree of immunosuppression. This study appraised the impact of HIV infection on clini­cal, laboratory and radiological presentations of tuberculosis."nMethods: The clinical, laboratory and radiological presentations of pulmonary TB in 56 HIV-infected patients were com­pared with 56 individually sex and age matched HIV-seronegative ones, admitted to Imam Hospital in Tehran (1999-2006) us­ing paired t-test in a case control study.  "nResults: All cases and the controls were male. Fever was found in 83.9% of the HIV positive patients compared to 80% of the HIV negative ones. Cough was the most common clinical finding in the HIV negative group (89.3% vs. 82.1% in HIV posi­tive group). Among radiological features, cavitary lesions, upper lobe and bilateral pulmonary involvement were ob­served significantly less often in the HIV-infected group. On the contrary, lymphadenopathy was just present in the HIV posi­tive group in this series of patients (12%) and primary pattern tuberculosis was more common, as well (71% vs. 39%, P= 0.02). The Tuberculin test was reactive in 29% of the HIV/TB patients."nConclusion: The coexistence of both infections alters the picture of tuberculosis in many aspects and should be taken into ac­count when considering a diagnosis of HIV infection and its potential for TB co-infection, and vice-versa. &nbsp

Study of 17 patients with Tuberculosis and HIV infection

Tuberculosis is an important opportunistic disease among HIV- infected persons worldwide; from March 1999 to Feburery 2001 we had seventeen patients with HIV-infection and tuberculosis. Here we are presenting the clinical manifestations, diagnosis, treatment and outcome of them. All of them were male, 11 patients had pulmonary and 5 patients had extrapulmonary (pleural effusion 1, hepatic granulomatosis 1, lymphadenopathy 3), one patient had pulmonary and polyserositis tuberculosis. Tuberculin skin test was positive in 6 paitents and only six patients had CD4 cell count at the beginning of their diseas, thirteen patients had positive smear for acid fast bacilli and four paitents had pathology compatible with tuberculosis (caseating granulomatous). Three patients were hemophiliac, nine patients were injecting drug users, fourteen paitents were treated with 6 months regimens and five patients died. Six patients had the scar of BCG vaccination and others did not know anyting about it

Peripheral Blood Mononuclear Cell Mycobacterium tuberculosis PCR sensitivity in diagnosis of Tuberculosis

Background: Tuberculosis is still one of the most important causes of mortality and morbidity in many countries and is the second only to human immunodeficiency virus as a cause of death worldwide resulting from a single infectious agent. In 1993, the World Health Organization declared tuberculosis a global public health emergency. Conven-tional methods for the diagnosis of Mycobacterium tuberculosis (MTB) infections are time consuming, as MTB culture requires 3-8 weeks for growth. To determine the sensitivity of polymerase chain reaction (PCR) in peripheral blood mononuclear cells (PBMC), we have evaluated Mycobacterium tuberculosis DNA in peripheral blood samples with PCR technique in adults with new cases of pulmonary and extra-pulmonary tuberculosis. Setting: Department of Infectious disease of Imam Khomeini Hospital, 2004- 2005, Tehran, Iran.Methods: In this cross-sectional study, we evaluated MTB DNA extracted from 3ml citrated peripheral blood samples from 95 adults with new cases of pulmonary and extra-pulmonary tuberculosis. DNA extraction was performed using a commercial PCR kit with IS1081 primers. For prevention of cross contamination and reduction of false positives, all steps were performed under laminar hood.Results: The 95 patients, 59 of whom were male, had a mean age 44.44 years (SD±20.26); 69 cases had pulmonary and 26 had extra-pulmonary tuberculosis. PCR was positive in 32 (33.7%) patients and negative in 63 (66.3%) cases. The overall sensitivity and accuracy of the PCR assay was 44.1% for pulmonary, 19.2% for extra-pulmonary and 10% for disseminated tuberculosis, respectively.Conclusion: The low sensitivity of the IS1081 primer MTB-PCR assay on PBMC may pose problems for the rapid diagnosis of tuberculosis. However, further studies are needed to confirm this technique as an alternative test for the diagnosis of tuberculosis