Self-assembly from milli- to nanoscales: methods and applications

The design and fabrication techniques for microelectromechanical systems (MEMS) and nanodevices are progressing rapidly. However, due to material and process flow incompatibilities in the fabrication of sensors, actuators and electronic circuitry, a final packaging step is often necessary to integrate all components of a heterogeneous microsystem on a common substrate. Robotic pick-and-place, although accurate and reliable at larger scales, is a serial process that downscales unfavorably due to stiction problems, fragility and sheer number of components. Self-assembly, on the other hand, is parallel and can be used for device sizes ranging from millimeters to nanometers. In this review, the state-of-the-art in methods and applications for self-assembly is reviewed. Methods for assembling three-dimensional (3D) MEMS structures out of two-dimensional (2D) ones are described. The use of capillary forces for folding 2D plates into 3D structures, as well as assembling parts onto a common substrate or aggregating parts to each other into 2D or 3D structures, is discussed. Shape matching and guided assembly by magnetic forces and electric fields are also reviewed. Finally, colloidal self-assembly and DNA-based self-assembly, mainly used at the nanoscale, are surveyed, and aspects of theoretical modeling of stochastic assembly processes are discussed.

Antimicrobial susceptibility pattern of microorganisms involved in the pathogenesis of surgical site infection (SSI); A 1 year of surveillance

The aim of this study is to identify the antibiotic sensitivity pattern of pathogens involved in the process of surgical site infection, in surgical wards. Changes made in the pattern of antibiotic use will result in different microorganism susceptibility patterns, which needs correct determination for precise empiric antibiotic therapy. One thousand patients (62% men and 38% women, 18- 74-years-old, with mean age 43 +/- 8)) who underwent surgical treatment, in Alzahra University Hospital, Isfahan University of Medicine, Isfahan, Iran, were studied from 2005 to 2006. Surgical wound infections, based on the reported criteria, were aspirated for culturing within 1 plus gram staining of prepared smears. Minimum Inhibitory Concentrations (MICs) were determined for samples and all derived data were compared by SPSS 13 and WHO net 5 software. The prevalence of SSI was 13.3% with 150 positive cultures, totally. Of 150 bacteria, isolated from surgical site infections Staphylococcus aureus had most frequency (43%). Resistance of isolated organisms was 41.7% in amikacin, 65 and 78.6% in ceftazidime, 85.7% in ceftriaxone, 61.5% in ciprofloxacin, 78.8% in gentamicine, 6.4% in imipenem, 13% in meropenem and 70.6% in trimethoprim/sulfamethoxazole, respectively. 78.9% of Staphylococcus aureus isolates were MRSA and vancomycine was the most effective antibiotic without any resistance. Among 10 isolates of coagulase negative Staphylococcus, no vancomycine resistance was seen, but in contrast all cases were resistant to oxacillin. The most common gram negative organism was Klebsiella (18 isolates) in which 100 and 80% were sensitive to imipenem and meropenem, respectively. Seventeen cases were E. coli, in which the most sensitivity was to meropenem (80%) and imipenem (77.8%). Thirteen cases of Pseudomonas were detected, in which 16.7% were resistant to imipenem and 8.3% to meropenem. Our results demonstrated that the total antibiotic resistance is increasing among SSIs, with an up sloping pattern, which will contact with a constant empiric antibiotic therapy. So, precise up to date antibiogram tantalize us toward balancing the rate of total antibiotic resistance to SSIs.

Role of clinical and ultrasound findings in the diagnosis of retained products of conception

OBJECTIVE

To assess the role of clinical and ultrasound findings as predictors of retained products of conception (RPOC) in women with a suspicion of incomplete miscarriage.

METHODS

This was a retrospective study of 91 patients admitted for suspected RPOC after spontaneous first-trimester miscarriage who were evacuated surgically, and for whom histopathological reports were available. All the women underwent transvaginal sonography after their miscarriage. The decision to evacuate the uterus was based on vaginal bleeding, lower abdominal pain and/or sonographic findings of hyperechoic material or endometrial thickness more than 8 mm. Maternal age, gestational age, clinical signs and symptoms and sonographic findings were recorded. Clinical and sonographic findings were compared with the histopathological reports and the sensitivity and specificity of vaginal bleeding, abdominal pain and sonographic appearance of the endometrium for detecting the products of conception were assessed.

RESULTS

Histopathological analysis confirmed the presence of chorionic villi in 55 women (60%) and decidua in 36 (40%). Vaginal bleeding was more frequent in women with RPOC (P < 0.001), whilst lower abdominal pain was a more frequent symptom in those with decidua (P = 0.019). The ultrasound finding of hyperechoic material had a sensitivity of 78%, specificity of 100% and positive and negative predictive values of 100% and 75%, respectively, in predicting RPOC. Vaginal bleeding as a predictor of RPOC had a sensitivity of 93%, specificity of 50%, and positive and negative predictive values of 74% and 82%, respectively. The combination of hyperechoic material and/or vaginal bleeding increased the sensitivity to 98% and negative predictive value to 95%. There was no significant difference in endometrial thickness between the two groups.

CONCLUSION

The ultrasound finding of hyperechoic material is the best predictor for diagnosing RPOC. In the absence of hyperechoic material and vaginal bleeding, RPOC are extremely unlikely.

Catalytic-kinetic determination of trace amount of formaldehyde by the spectrophotometric method with a bromate-Janus green system

A new simple and rapid catalytic kinetic method for the determination of trace amount of formaldehyde is described. The method is based on the catalytic effect of formaldehyde on the oxidation of Janus green by bromate in the present of sulfuric acid. The reaction monitored spectrophotometrically by measuring the decrease in absorbance of the reaction mixture at 618 nm. The fixed-time method was used for the first 150 s. For initiation of the reaction, under the optimum conditions, in the concentration range of 0.003-2.5 microg ml(-1) formaldehyde can be determined with a limit of detection 0.0015 microg ml(-1). The relative standard deviation of five replicate measurements is 2.3% for 1.0 microg ml(-1) of formaldehyde. The method was used for the determination of formaldehyde in real samples with satisfactory results.

Can WHO therapy failure criteria for non-severe pneumonia be improved in children aged 2-59 months?

SETTING

In the recent past, there have been reports of rising treatment failure rates for non-severe pneumonia. It is felt that World Health Organization (WHO) criteria for therapy failure are too sensitive and that many children are unnecessarily classified as failures. We studied alternative, less sensitive therapy failure criteria.

METHODS

In this nested study we followed the clinical course of non-severe pneumonia in children aged 2-59 months using alternative therapy failure criteria. All children received amoxicillin and were followed up on days 3, 5 and 14 after enrollment. On day 3, children were labelled as therapy failure only if their condition had deteriorated. These failure rates were compared with those using WHO definitions.

RESULTS

During the study period, 876 children with non-severe pneumonia were followed up until day 14. On day 3, using alternative therapy failure criteria, 31 (3.5%) children were labelled as therapy failure compared to 95 (10.8%) using current WHO criteria. The difference was statistically significant (P = 0.001).

CONCLUSIONS

The alternative therapy failure criteria work reasonably well, without causing any higher risk to children with non-severe pneumonia. Antibiotics should be changed only in those children who show signs of deterioration on day 3. This would prevent unnecessary changes in antibiotic treatment in many children.

mTOR: a placental growth signaling sensor

The proliferation and differentiation of trophoblast cells is under the control of a variety of hormones and growth factors and is influenced by nutrient availability. The intracellular signaling pathways acting downstream of these mitogenic factors and nutrients to regulate trophoblast proliferation and placental development are poorly understood. Immortalized human trophoblast cells were used (HTR-8/SVneo) to investigate trophoblast proliferation in response to angiopoietin-2 (Ang-2), a major angiogenic factor and glucose (a major nutrient). Trophoblast cell proliferation was induced through activation of the phosphatidylinositol-3 (PI-3) kinase and the mammalian target of rapamycin (mTOR) signaling pathways, following Tie-2 receptor activation. Glucose also stimulated trophoblast cell proliferation through mTOR signaling. Ang-2 activated mTOR via PI-3 kinase-dependent signaling; whereas glucose-mediated mTOR activation was PI-3 kinase-independent and involved a novel nutrient sensor, glutamine fructose-6-phosphate amidotransferase (GFAT). Metabolites of the GFAT reaction acted upstream of mTOR and functioned as a nutrient sensor to regulate trophoblast cell proliferation in response to glucose. Overall, the results show that growth factor and nutrient signaling converge at tuberin, an upstream regulator of mTOR and that mTOR functions as an important placental growth signaling sensor. These results are the first to link mTOR with GFAT metabolites as nutrient sensors for trophoblast cell proliferation.

Phenotypic features of myoclonus-dystonia in three kindreds

BACKGROUND

Myoclonus-dystonia (M-D) is a movement disorder with involuntary jerks and dystonic contractions. Autosomal dominant alcohol-responsive M-D is associated with mutations in the epsilon-sarcoglycan gene (SGCE) (six families) and with a missense change in the D2 dopamine receptor (DRD2)gene (one family).

OBJECTIVE

To investigate the clinical phenotype associated with M-D including motor symptoms, psychiatric disorders, and neuropsychological deficits.

METHODS

Fifty individuals in three M-D families were evaluated and a standardized neurologic examination and DNA analysis were performed. Psychiatric profiles were established with the Diagnostic Interviews for Genetic Studies (DIGS) and the Yale-Brown Obsessive-Compulsive Scale (YBOCS). Cognition was evaluated with standardized neuropsychological tests.

RESULTS

Distinct truncating mutations in the SGCE gene were identified in each family. Additionally, a missense alteration in the DRD2 gene was previously found in one family. Motor expression was variable, with onset of myoclonus or dystonia or both affecting the upper body and progression to myoclonus and dystonia in most cases. Psychiatric profiles revealed depression, obsessive-compulsive disorder, substance abuse, anxiety/panic/phobic disorders, and psychosis in two families, and depression only in the third family. Averaged scores from cognitive testing showed impaired verbal learning and memory in one family, impaired memory in the second family, and no cognitive deficits in the third family.

CONCLUSIONS

Cognitive deficits may be associated with M-D. Psychiatric abnormalities correlate with the motor symptoms in affected individuals. Assessment of additional M-D families with known mutations is needed to determine whether these are characteristic phenotypic manifestations of M-D.

Hypoxia in vivo decreases peroxisome proliferator-activated receptor alpha-regulated gene expression in rat heart

We tested the hypothesis that hypoxia decreases PPARalpha-regulated gene expression in heart muscle in vivo. In two rat models of systemic hypoxia (cobalt chloride treatment and iso-volemic hemodilution), transcript levels of PPARalpha and PPARalpha-regulated genes (pyruvate dehydrogenase kinase 4 (PDK4), muscle carnitine palmitoyltransferase-I (mCPT-I), and malonyl-CoA decarboxylase (MCD)) were measured using real-time quantitative RT-PCR. Data were normalized to the housekeeping gene beta-actin. Atrial natriuretic factor (ANF) and pyruvate dehydrogenase kinase 2 (PDK2), which are not regulated by PPARalpha, served as controls. CoCl(2) treatment decreased PPARalpha, PDK4, mCPT-I, and MCD mRNA levels. Iso-volemic anemia also caused a significant decrease in PPARalpha, PDK4, and MCD mRNA levels. Transcript levels of mCPT-I showed a slight, but not significant decrease (P = 0.08). Gene expression of beta-actin, ANF, and PDK2 did not change with either CoCl(2) treatment nor with anemia. Myocardial PPARalpha-regulated gene expression is decreased in two models of hypoxia in vivo. These results suggest a transcriptional mechanism for decreased fatty oxidation and increased reliance of the heart for glucose during hypoxia.

Kinetic spectrophotometric method for the determination of oxalic acid by its catalytic effect on the oxidation of safranine by dichromate

A new catalytic kinetic spectrophotometric method for the determination of oxalic acid has been described based on its catalytic effect on the redox reaction between safranine and dichromate in dilute sulfuric acid media. The reaction is monitored photometrically by measuring the decrease in absorbance of safranine at the maximum wavelength of 530 nm. Under the optimum conditions, a calibration graph from 0.10 to 10.00 microg ml(-1) of oxalic acid with a detection limit of 0.08 microg ml(-1) was obtained. The relative standard deviation (R.S.D.) for ten replicate measurements of 1.0 and 5.0 microg ml(-1) oxalic acid was 2.7 and 2.5%, respectively. The purposed method is simple, sensitive, selective and inexpensive. The applicability of the proposed method was determined by the determination of oxalic acid in spinach and wastewater samples with satisfactory results.

Differential pulse adsorption stripping voltammetric determination of copper(II) with 2-mercaptobenzimidazol at a hanging mercury-drop electrode

Copper(II) was selectively accumulated on a hanging mercury-drop electrode by using 2-mercaptobenzimidazole. Ensuing measurements were carried out by differential pulse adsorption stripping voltammetry. Factors affecting the accumulation, reduction, and stripping steps were investigated and a procedure was developed. The optimum conditions for the analysis of copper were pH 5.0, 5.33 x 10(-5) M 2-mercaptobenzimidazole and an accumulation potential of -0.10 V (vs. Av/AgCl). A linear range was obtained in the concentration range 0.2-100 ng/ml with a 90 s accumulation time and a scan rate of 16 mV/s. For ten successive determinations of 1.0, 20.0 and 70.0 ng/ml copper(II), relative standard deviations of 4.2, 3.5 and 2.8%, respectively, were obtained. The developed method was applied to the determination of copper in commercial salts and aluminium alloys.

Prolonged fetal ritodrine exposure and immediate neonatal outcome

Ritodrine hydrochloride was administered over a period of two years to a total of 200 women in premature labor. One hundred sixty-two (81 per cent) of the women carried pregnancy to 35 weeks or longer. To determine the effect of ritodrine on the neonates, the duration and amount of exposure, onset of exposure, and interval between cessation of exposure and delivery were correlated with gestational age, birth weight, Apgar scores, mortality, and the presence of hypoglycemia, hyperbilirubinemia, respiratory distress, and intrauterine growth retardation. Infants exposed for six weeks or more (long-term exposure) were significantly heavier than those exposed for shorter periods (short-term exposure), a difference that was possibly attributable to differences in gestational age at birth. Infants who were exposed as fetuses to ritodrine beginning at 30 weeks' or less gestation needed phototherapy more often than did infants whose fetal exposure began at after 30 weeks' gestation. Neither duration of exposure nor gestational age at birth was a significant factor in hyperbilirubinemia. Of infants delivered at or after 35 weeks' gestation, 32 (20 per cent) experienced early hypoglycemia; and 26 of these (81 per cent) were exposed up to the day of delivery. This outcome differed significantly from that of infants whose exposure stopped at least one week before delivery. In addition, respiratory distress syndrome was more common in those infants exposed up until delivery (34 of 36).(ABSTRACT TRUNCATED AT 250 WORDS)

Affine-similar shape retrieval: application to multiview 3-D object recognition

The feasibility of representing a three-dimensional (3-D) object with a small number of standard views is studied. The object boundary of each view is considered as a two dimensional (2-D) shape and is represented by the locations of the maxima of its curvature scale space (CSS) image contours. The idea is to identify an unknown object from an image taken from a random view by using the stored descriptions of the standard views. The CSS image has been selected for MPEG-7 standardization. The maxima of CSS image have already been used to represent 2-D shapes in different applications under similarity transforms. Since the new application involves affine transforms, we first examine the effects of general affine transforms on the representation and show that the locations of the maxima of the CSS image do not move dramatically even under large affine transformations. Our system for shape-based retrieval from large image databases is then applied to multiview 3-D object representation and recognition. Our collection of 3-D objects consists of 18 aircraft of different shapes. Three silhouette contours corresponding to random views are separately used as input for each object. Results indicate that robust and efficient 3-D free-form object recognition through multiview representation can be achieved using the CSS representation.

Effects of early inhaled beclomethasone therapy on tracheal aspirate inflammatory mediators IL-8 and IL-1ra in ventilated preterm infants at risk for bronchopulmonary dysplasia

We tested the hypothesis that inhaled beclomethasone therapy for prevention of bronchopulmonary dysplasia (BPD) reduces pulmonary inflammation. As part of a randomized, placebo-controlled trial, interleukin-8 (IL-8) and interleukin-1 receptor antagonist (IL-1ra) concentrations in tracheal aspirates were measured as markers of pulmonary inflammation. On study days 1 (baseline), 8, 15, and day 28 of age, samples were obtained from enrolled infants (birth weights <1,251 g, gestational age <33 week, 3 to 14 days of age) who remained ventilated and had not received systemic glucocorticoid therapy. Cytokine levels (pg/microg of free secretory component of immunoglobulin A) were compared between groups. We determined whether baseline cytokine levels modified treatment effect regarding subsequent need for systemic glucocorticoid therapy or occurrence of BPD (age 28 days). Tracheal aspirates were obtained from 161 infants (77 receiving beclomethasone, 84 receiving placebo). Median IL-8 levels were lower in beclomethasone versus placebo infants on study days 8 (82.9 vs. 209.2, P < 0.01) and 15 (37.4 vs. 77.4, P < 0.03) after controlling for antenatal glucocorticoid therapy and maternal race. Median IL-1ra levels were lower in beclomethasone versus placebo infants only on study day 8 (86.5 vs. 153.3, P < 0.01). Fewer beclomethasone infants with baseline IL-8 levels in the interquartile range required systemic glucocorticoid therapy (beclomethasone 30.6% vs. placebo 65.8%, P < 0.01) or developed BPD (beclomethasone 42.4% vs. placebo 69.4%, P < 0.03). We conclude that early-inhaled beclomethasone therapy was associated with a reduction in pulmonary inflammation after 1 week of therapy. Beclomethasone-treated infants with moderately elevated baseline IL-8 levels received less subsequent systemic glucocorticoid therapy and had a lower incidence of BPD than nontreated infants.