Geometric Conformability of 3D Concrete Printing Mixtures from a Rheological Perspective

The effectiveness of 3D concrete printing (3DCP) relies on understanding the rheological properties of cementitious materials and their time-dependent evolution. These materials exhibit shear-thinning viscosity, an elastic region, and both static and dynamic yield stress, which are challenging to balance in 3DCP. Layer deformation can be caused by factors such as self-weight, the weight of subsequently deposited layers, and the stress induced by the nozzle pressing. Starting at the level of a single filament, the final geometrical conformity of a 3D-printed object is the sum of individual filament conformities. Hence, the control of layer deformation during the printing process is critical. The failure of 3D-printed objects can occur due to two primary mechanisms: material failure, which occurs when the material's strength is exceeded, resulting in fracture or uncontrolled deformation; and stability failure, where the object cannot retain equilibrium of forces. These mechanisms often interact; extensive deformations resulting from material failure can lead to stability loss, or conversely, stability loss generates local excessive stresses leading to material failure. The governing mechanism depends on various factors, including material and process characteristics, as well as the transient nature of material properties, print strategy, and object design. With this in mind, this research aimed to broaden the understanding of the connection between rheological material properties-primarily yield stress-and the geometric conformability of printed objects. Experimental tests were conducted on pastes using a rheometer, and correlated mortars, allowing for the evaluation of realistic extrusion properties.

Probability Density Function Models for Float Glass under Mechanical Loading with Varying Parameters

Glass as a construction material has become indispensable and is still on the rise in the building industry. However, there is still a need for numerical models that can predict the strength of structural glass in different configurations. The complexity lies in the failure of glass elements largely driven by pre-existing microscopic surface flaws. These flaws are present over the entire glass surface, and the properties of each flaw vary. Therefore, the fracture strength of glass is described by a probability function and will depend on the size of the panels, the loading conditions and the flaw size distribution. This paper extends the strength prediction model of Osnes et al. with the model selection by the Akaike information criterion. This allows us to determine the most appropriate probability density function describing the glass panel strength. The analyses indicate that the most appropriate model is mainly affected by the number of flaws subjected to the maximum tensile stresses. When many flaws are loaded, the strength is better described by a normal or Weibull distribution. When few flaws are loaded, the distribution tends more towards a Gumbel distribution. A parameter study is performed to examine the most important and influencing parameters in the strength prediction model.

Immunological stimuli change expression of genes and neutrophil function in fathead minnow Pimephales promelas Rafinesque

Fathead minnows Pimephales promelas were exposed to lipopolysaccharide (LPS) and polyinosinic-polycytidylic acid [poly(I:C)] to observe immunological responses during simulated bacterial and viral challenge at the level of gene expression and granulocyte function. Complementary DNA libraries were created from LPS- and poly(I:C)-treated fish and c. 5000 expressed sequence tags (ESTs) were sequenced. The ESTs were subjected to BLASTx analysis and 1500 genes were annotated, grouped by function and 20 immune genes were selected for expression studies by real-time PCR. Lipopolysaccharide treatment significantly downregulated expression of interferon regulatory factor 2 binding protein 1 (nine-fold), Chemokine (C-X-C motif) ligand 12a (three-fold) and TNF-related apoptosis-inducing ligand, TRAIL (two-fold). In poly(I:C)-treated fish, a significant upregulation was observed for IFN-inducible and antiviral proteins belonging to the family of Mx proteins (73-fold) and chemokine CCL-C5a (28-fold). Blood neutrophil count was significantly increased in poly(I:C)-treated fish at 24 and 48 h post-injection. Neutrophil extracellular trap release and respiratory burst of kidney granulocytes were suppressed in poly(I:C)-treated fish, while degranulation of primary granules was not affected significantly by the treatment. The changes in gene expression and neutrophil function in P. promelas exposed to LPS and poly(I:C) support the use of this species as an alternative model for studies of pathogen effects on the innate immune system of fishes.

Probability of bystander effect induced by alpha-particles emitted by radon progeny using the analytical model of tracheobronchial tree

Radiation-induced biological bystander effects have become a phenomenon associated with the interaction of radiation with cells. There is a need to include the influence of biological effects in the dosimetry of the human lung. With this aim, the purpose of this work is to calculate the probability of bystander effect induced by alpha-particle radiation on sensitive cells of the human lung. Probability was calculated by applying the analytical model cylinder bifurcation, which was created to simulate the geometry of the human lung with the geometric distribution of cell nuclei in the airway wall of the tracheobronchial tree. This analytical model of the human tracheobronchial tree represents the extension of the ICRP 66 model, and follows it as much as possible. Reported probabilities are calculated for various targets and alpha-particle energies. Probability of bystander effect has been calculated for alpha particles with 6 and 7.69 MeV energies, which are emitted in the (222)Rn chain. The application of these results may enhance current dose risk estimation approaches in the sense of the inclusion of the influence of the biological effects.

[Results of epidemiological surveillance of hospital infections at the Clinic of Digestive System Surgery, CCS, in 2007]

INTRODUCTION

Nosocomial infections (NI) are significant medical problem in the countries worldwide. NI significance reflects in higher morbidity and mortality rates, and moreover, NIs add to longer stay and higher treatment costs. Based on data obtained from underdeveloped and developing countries, over 20% of hospitalized patients acquire some of NIs, while that proportion is 5% in developed countries.

OBJECTIVE

A) to establish the frequency of noosocomial infections at the Clinic of Digestive System Diseases, b) determine the NI incidence in accord with anatomic localizations, c) evaluate the percentage prevalence of NI causes according to anatomic localizations, and d) review the problem of resistance of NI causative agents.

MATERIAL AND METHODS

The study of NI incidence was calculated by Center for Diseases and Prevention (CDC) methodology. Sampling, cultivation, isolation, identification and sensitivity tests of cauosative agents to antimicrobial drugs, obtained from patient's material, were carried out by standard microbiological methods in Microbiological laboratory of the Emergency Center, Clinical Center of Serbia. All infections in patients hospitalized at the Clinic of Digestive System Surgery in 2007 were recorded. Data available from medical documentation as well as data obtained from interviews of medical personnel were analyzed.

RESULTS

The incidence rates of patients with NI ranged from 1.7-3.4 per 1000 hospital days. Out of a total number of recorded nosocomial infections, surgical site infections accounted for 69%, blood infections 23% and urinary tract infections 6.8%. The most frequent causative agents of surgical site infections in the last year were as follows: Pseudomonas spp (19%), followed by Staphylococcus aureus and Klebsiella spp--(18%), Acinetobacter spp (13%), and Enterococcus spp (8%). Forty percent (40%) of all blood infections verified by laboratory tests in 2007 was caused by coagulase negative Staphylococcus spp (CNS), followed by Acinetobacter spp (18%). Enterococcus spp (11%), and Staphylococcus aureus (7%). The most frequent causative agents of urinary infections were: Escherichia coli (35%) and Enterococcus spp (29%). Over 80% of Staphylococcus aureus isolates were resistant to Methicillin (MRSA) and enterobacteria produced by beta lactamase were recorded (ESBL).

CONCLUSION

Enforcement of epidemiological surveillance of nosocomial infections contributes to insight of severity of NI problem, recognition of resistance of causative agents to antibiotics and recommendation of specific preventive measures related to these infections.

[Management of cadaveric organ donors]

Because the supply of cadaveric organ donors is limited and their ICU management is complex, a multidisciplinary, well-coordinated, and institutionally supported approach to management is essential to ensure the maintenance of the current supply and to increase the future supply of organs and tissues that are suitable for transplantation. The potential organ donor is at high risk for instability as a direct consequence of the loss of physiologic homeostatic mechanisms that are dependent on functioning of the central nervous system. The keys to successful ICU management of the potential organ donor include a team approach that is focused on the anticipation of complications, appropriate physiologic monitoring, aggressive life support, with frequent reassessment and titration of therapy.

[Coagulopaty in associated with massive transfusion]

Massive hemorrhage is a formidable challenge for anesthesia care providers in the elective setting and poses even greater potential challenges in the trauma setting. In all this cases, the anesthesia care providers are faced with large-volume resuscitations that typically start with crystalloid and colloid and rapidly progress to blood and blood products. These large-volume replacement may cause coagulopathy, which can be difficult to manage in the setting of ongoing blood loss. Coagulopathy associated with massive transfusion is multifactorial event that results from hemodilution, hypothermia, the use of fractionated blood products and disseminated intravascular coagulation. Maintaining a normal body temperature is a first-line, effective strategy to improve hemostasis during massive transfusion. Treatment strategies include the maintenance of adequate tissue perfusion, the corection of anemia, and the use of hemostatic blood products.

[Hemorrhagic shock]

Hemorrhagic shock is a condition produced by rapid and significant loss of blood which lead to hemodynamic instability, decreases in oxygen delivery, decreased tissue perfusion, cellular hypoxia, organ damage and can be rapidly fatal. Despite improved understanding of the pathophysiology and significant advances in technology, it remains a serious problem associated with high morbidity and mortality. Early treatment is essential but is hampered by the fact that signs and symptoms of shock appear only after the state of shock is well establish and the compensatory mechanisms have started to fail. The primary goal is to stop the bleeding and restore the intravascular volume. This review addresses the pathophysiology and treatment of haemorrhagic shock.

[Direct laryngomicroscopy from 1984 to 1993 at the Department of Ear, Nose and Throat Diseases at the General Hospital in Subotica]

A retrospective analysis is presented of laryngomicroscopic examinations in the period 1984-1993. Examinations were performed on 577 patients of different age and of both sexes. In 449 patients histopathologic examination revealed pathologic changes of the tissue, whereas in 128 patients histopathologic analysis was not performed. By statistical data analysis malignant pharyngeal tumor was established in 65 patients (14.48%); precancerous changes in 100 patients (22.27%), while the rest of patients-284 (63.25%) had benign laryngeal changes.

Enteroaggregative Escherichia coli associated with an outbreak of diarrhoea in a neonatal nursery ward

Over a 9-day period in February 1995, 16 newborn babies (age range 2-11 days) and 3 infants (24, 47 and 180 days of age) in a neonatal nursery ward developed diarrhoea accompanied by pyrexia and weight loss. Known enteropathogens were not detected in their stools but Escherichia coli displaying aggregative adherence to HEp-2 cells (enteroaggregative E. coli) were found in 12 (63%) ill infants and in none of 5 well neonates (P = 0.02). The illness lasted 3-9 days (mean 5.2) in 16 babies, whereas in 3 neonates it showed a protracted course of 18-20 days. The source of infection and the mode of transmission remained unclear. The outbreak isolates manifested properties common in this new group of diarrhoeagenic E. coli: mannose-resistant haemagglutination, haemolysis on blood agar, and clump formation in liquid culture medium. They belonged to the O4 E. coli serogroup and expressed multiple antibiotic resistance.

[Management of war injuries in Vukovar]

During 42 days of combat operations the brigade medical station provided surgical care for 535 wounded. One third of the wounded (31.8%) were classified in I or II grade of emergency. In the units were returned 21.7% of the wounded. Infusion therapy was applied in 47%. Laparotomy was performed in 7, drainage of the chest cavity in 19 and guillotine amputation of extremities in 11 wounded. The mortality was 1.9% at this stage. The way of management was imposed by combat operations, manpower and means available.

[Megacolon congenitum (Hirschsprung's disease) in adults]

Hirschsprung's disease is rare in adults and represents a unique problem in the diagnosis and therapy. The permanent symptoms of the disease are persistent chronic constipation and meteorism. The degree of constipation depends on the length and narrowing of the aganglionary segment, diet and compensatory capacities of the bowel. Already known characteristics of agangliosis (absence of ganglions cells in intramuscular and submucous plexus, changes in nerve fibers and increased cholinesterase activity of the parasympathetic nerve fibers) cause impairment in peristalsis of the aganglionary segment and insufficient relaxation of the internal anal sphincter. The result is a functional refractory constipation. The disease can be diagnosed on the basis of the history, RTG examination, electromanometry and histopathology. In the majority of cases RTG examination is very reliable if performed according to generally accepted criteria. It is important to reveal the narrowed aganglionary area by oblique and profile images during irrigoscopy and irrigography. The treatment is surgical. The preferred operations are those with a combined transabdominal-transanal approach. Such operations are the most successful in management of constipation and maintenance of contingency. The authors present three cases. Three patients were old between 21 and 23 years. Their stools ranged from 10 days to two months (a stool per 10 days to two months). The diagnosis was established for all three patients by RTG examinations and histopathological findings. All bore the operation very successfully. Three various operation techniques were used according to surgeon's choice.