Thermal stabilities and flame retardancies of phloroglucinol‐based organo phosphates when applied to polycarbonate

A series of organo phosphorus flame retardants (FRs) based on aromatic phosphate and cyclic phosphate were synthesized in an attempt to develop an efficient FR for polycarbonate. Their successful synthesis was confirmed by FT‐IR and ¹ H and ³¹P NMR. Their thermal stability and flame retarding efficiency as a single‐component additive were investigated and compared with the commercial FR, resorcinol bis(diphenyl phosphate). The thermogravimetric analysis results revealed that the aromatic phosphate synthesized in this study, phloroglucinol diphenyl phosphate (PDP), shows a higher thermal degradation temperature and better flame retardancy even though it has a lower P content than cyclic phosphate‐based FRs. The flame retarding efficiency was evaluated by the UL‐94 test method. The V‐0 rating was achieved at a PDP loading of 2 wt% in polycarbonate in the presence of an anti‐dripping agent (1 wt%), which is better than that of resorcinol bis(diphenyl phosphate) and cyclic phosphate‐based FRs. The high thermal stability and P–OH generation tendency is responsible for the better flame‐retarding performance of PDP. The degradation path of PDP is also discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Coherent Dynamics of Localized Spins in an Inhomogeneous Magnetic Field

We studied the influence of the inhomogeneity of fringe fields originating from nanostructured ferromagnets on the coherent dynamics of localized Mn²⁺ spins in a (Zn,Cd,Mn)Se/ZnSe quantum well by time-resolved Kerr rotation. By studying hybrid systems with different geometry, we demonstrate that the spatially inhomogeneous fringe field results in two main consequences for the localized spin system: First, a temporal variation of the ensemble precession frequency is obtained, and second, a reduced ensemble spin dephasing time T ₂^* is observed in comparison to an unstructured reference area of the sample.     

Time to clinical stability in patients hospitalized with community-acquired pneumonia: implications for practice guidelines

CONTEXT: Many groups have developed guidelines to shorten hospital length of stay in pneumonia in order to decrease costs, but the length of time until a patient hospitalized with pneumonia becomes clinically stable has not been established. OBJECTIVE: To describe the time to resolution of abnormalities in vital signs, ability to eat, and mental status in patients with community-acquired pneumonia and assess clinical outcomes after achieving stability. DESIGN: Prospective, multicenter, observational cohort study. SETTING: Three university and 1 community teaching hospital in Boston, Mass, Pittsburgh, Pa, and Halifax, Nova Scotia. PATIENTS: Six hundred eighty-six adults hospitalized with community-acquired pneumonia. MAIN OUTCOME MEASURES: Time to resolution of vital signs, ability to eat, mental status, hospital length of stay, and admission to an intensive care, coronary care, or telemetry unit. RESULTS: The median time to stability was 2 days for heart rate (< or =100 beats/min) and systolic blood pressure (> or =90 mm Hg), and 3 days for respiratory rate (< or =24 breaths/min), oxygen saturation (> or =90%), and temperature (< or =37.2 degrees C [99 degrees F]). The median time to overall clinical stability was 3 days for the most lenient definition of stability and 7 days for the most conservative definition. Patients with more severe cases of pneumonia at presentation took longer to reach stability. Once stability was achieved, clinical deterioration requiring intensive care, coronary care, or telemetry monitoring occurred in 1% of cases or fewer. Between 65% to 86% of patients stayed in the hospital more than 1 day after reaching stability, and fewer than 29% to 46% were converted to oral antibiotics within 1 day of stability, depending on the definition of stability. CONCLUSIONS: Our estimates of time to stability in pneumonia and explicit criteria for defining stability can provide an evidence-based estimate of optimal length of stay, and outline a clinically sensible approach to improving the efficiency of inpatient management.     

Chemical vapor synthesis of size-selected zinc oxide nanoparticles

ZnO can be regarded as one of the most important metal oxide semiconductors for future applications. Similar to silicon in microelectronics, it is not only important to obtain nanoscale building blocks of ZnO, but also extraordinary purity has to be ensured. A new gas-phase approach to obtain size-selected, nanocrystalline ZnO particles is presented. The tetrameric alkyl-alkoxy zinc compound [CH(3)ZnOCH(CH(3))(2)](4) is chemically transformed into ZnO, and the mechanism of gas-phase transformation is studied in detail. Furthermore, the morphological genesis of particles via gas-phase sintering is investigated, and for the first time a detailed model of the gas-phase sintering processes of ZnO is presented. Various analytical techniques (powder XRD, TEM/energy-dispersive X-ray spectroscopy, magic-angle spinning NMR spectroscopy, FTIR spectroscopy, etc.) are used to investigate the structure and purity of the samples. In particular, the defect structure of the ZnO was studied by photoluminescence spectroscopy.     

Characteristic Dependency of Hydrogen-Affected Fatigue Crack Growth and Crack Tip Plasticity on Low Loading Frequency in α-Iron

Metallurgical and Materials Transactions A - Aiming to investigate the dependency of hydrogen-affected fatigue crack growth (HAFCG) on the loading frequency f, this study experimentally...     

Fatigue Crack Growth under High Pressure of Gaseous Hydrogen in a 15-5PH Martensitic Stainless Steel: Influence of Pressure and Loading Frequency

In this study, the effect of gaseous hydrogen pressure in relation with the loading frequency on the fatigue crack growth behavior of a precipitation-hardened martensitic stainless steel is investigated. It is found that increasing the hydrogen pressure from 0.09 to 9 MPa induces an enhancement of the fatigue crack growth rates. This enhancement is pronounced particularly at higher stress intensity factor amplitudes at 9 MPa. Meanwhile, decreasing the frequency from 20 to 0.2 Hz under 0.9 MPa of hydrogen reveals a significant increase in the crack growth rates that tends to join the curve obtained under 9 MPa at 20 Hz, but with a different cracking mode. However, it is shown that the degradation in fatigue crack growth behavior derives from a complex interaction between the fatigue damage and the amount of hydrogen enriching the crack tip, which is dependent on the hydrogen pressure, loading frequency, and stress intensity factor level. Scanning electron microscope (SEM) observations of the fracture surfaces are used to support the explanations proposed to account for the observed phenomena.     

Halm-Zielke instrumentation for primary stable anterior scoliosis surgery: operative technique and 2-year results in ten consecutive adolescent idiopathic scoliosis patients within a prospective clinical trial

OBJECTIVE: To determine the efficacy and safety of a new continence procedure, tension-free vaginal tape (TVT) placement for surgical treatment of stress urinary incontinence in women. STUDY DESIGN: Eighty-three women with demonstrable stress urinary incontinence underwent a nonrandomized, prospective study using the TVT procedure. The procedure was previously described by Ulmsten et al. In the present study, instead of local anesthesia, epidural blockade with 20 mL of 2% xylocaine was used. Preoperatively the patients were evaluated with a one-hour pad test, full urodynamic testing using either a double-lumen catheter or microtip transducer catheter and were instructed to maintain an one-week baseline urinary diary one week before and two months after the operation. Another one-hour pad test and complete urodynamic evaluation using microtip transducer catheters were offered to 20 patients postoperatively. The period of follow-up ranged from 3 to 18 months. RESULTS: Thirteen women were excluded for various reasons; thus, 70 subjects were enrolled in the study. The urodynamic diagnosis of the 83 women revealed that 71 had genuine stress incontinence, 11 had mixed incontinence and 1 was normal. Mean operation time was 29 minutes (range, 20-51) and mean hospital stay 3 days (range, 2-8). Three bladder perforations occurred intraoperatively. No patients had intraoperative bleeding > 300 mL, but 11 (16%) had blood loss > 200 mL, necessitating an indwelling catheter and vaginal tamponade. No evidence of defect healing or rejection of the tape occurred. Urine leakage observed on the pad test was significantly reduced from a mean of 63 g (range, 10-213) before to a mean of 5 g (range, 0-42) after surgery. The objective cure rate was 83%, and the subjective rate was 87%. CONCLUSION: Although the follow-up period was short, the TVT procedure seemed to be a safe and effective method for the treatment of stress urinary incontinence.     

Lactic acid tolerance determined by measurement of intracellular pH of single cells of Candida krusei and Saccharomyces cerevisiae isolated from fermented maize dough

Strains of Candida krusei and Saccharomyces cerevisiae were grown together at 30 degrees C in MYGP broth, pH 2.5, in the presence of 106.4 mM undissociated lactic acid. The two C. krusei strains investigated grew within 48 h from initial counts of 2 x 10(4) to approximately 10(7) cells/ml whereas the two S. cerevisiae strains investigated survived but did not grow in the presence of 106.4 mM undissociated lactic acid at pH 2.5. To explain the differences in lactic acid tolerance of the two yeast species, we used fluorescence-ratio-imaging microscopy and a perfusion system to determine the short-term intracellular pH (pH(i)) changes in single cells of C. krusei and S. cerevisiae. The changes were investigated both in the presence of low (20.7 mM) and high (106.4 mM) concentrations of undissociated lactic acid. For both the investigated species 20.7 mM undissociated lactic acid did not seem to influence the initial pH(i) which for C. krusei was found to be approximately 8.0 and for S. cerevisiae 6.9-7.5. For both C. krusei strains, perfusion with 106.4 mM undissociated lactic acid induced only weak short-term pH(i) responses with a decrease in pH(i) of less than one pH unit. Contrary, for both strains of S. cerevisiae perfusion with 106.4 mM undissociated lactic acid resulted in a significant decrease in pH(i) from initially 6.9-7.5 to 6.2-6.4 after 1 min and further to a pH(i) of < or = 5.5 after 3 min after which it remained constant. The results obtained show that C. krusei is more resistant to short-term pH(i) changes caused by lactic acid than S. cerevisiae, and this, in turn, may be part of the explanation why C. krusei is more tolerant to lactic acid than S. cerevisiae.