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Low Yield (low + yield)
Selected AbstractsEstimation of regional material yield from coastal landslides based on historical digital terrain modelling,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2005C. J. Hapke Abstract High-resolution historical (1942) and recent (1994) digital terrain models were derived from aerial photographs along the Big Sur coastline in central California to measure the long-term volume of material that enters the nearshore environment. During the 52-year measurement time period, an average of 21 000 ± 3100 m3 km,1 a,1 of material was eroded from nine study sections distributed along the coast, with a low yield of 1000 ± 240 m3 km,1 a,1 and a high of 46 700 ± 7300 m3 km,1 a,1. The results compare well with known volumes from several deep-seated landslides in the area and suggest that the processes by which material is delivered to the coast are episodic in nature. In addition, a number of parameters are investigated to determine what influences the substantial variation in yield along the coast. It is found that the magnitude of regional coastal landslide sediment yield is primarily related to the physical strength of the slope-forming material. Coastal Highway 1 runs along the lower portion of the slope along this stretch of coastline, and winter storms frequently damage the highway. The California Department of Transportation is responsible for maintaining this scenic highway while minimizing the impacts to the coastal ecosystems that are part of the Monterey Bay National Marine Sanctuary. This study provides environmental managers with critical background data on the volumes of material that historically enter the nearshore from landslides, as well as demonstrating the application of deriving historical digital terrain data to model landscape evolution. Published in 2005 by John Wiley & Sons, Ltd. [source] Is Transesophageal Echocardiography Necessary before D.C. Cardioversion in Patients with a Normal Transthoracic Echocardiogram?ECHOCARDIOGRAPHY, Issue 4 2007Mohsen Sharifi M.D. Purpose: Transesophageal echocardiography has emerged as an accepted approach before D.C. cardioversion for atrial fibrillation. The frequency of atrial thrombi detected on transesophageal echocardiography has varied from 7% to 23%. Many patients undergoing transesophageal echocardiography have had a previous transthoracic echocardiogram. Though transthoracic echocardiography has a low yield for the detection of intracardiac thrombi, it is highly accurate in diagnosing a structurally abnormal heart. The purpose of this study was to assess the frequency of thrombi detected by transesophageal echocardiography in patients with an entirely normal transthoracic echocardiogram and hence the advocacy of a selective approach in performing transesophageal echocardiography in patients undergoing D.C. cardioversion for atrial fibrillation. Methods: 112 consecutive patients with atrial fibrillation who had undergone transesophageal echocardiography before D.C. cardioversion were evaluated. They all had a transthoracic echocardiogram within the 2 months preceding their transesophageal echocardiogram. Based on their transthoracic echocardiographic study, they were divided into two groups: Group 1 consisted of patients with a normal transthoracic echocardiogram and Group 2, those with an abnormal study. Results: Thrombi or spontaneous echo contrast were found in 14 of 112 patients (16%). All however were detected in Group 2 patients. There was no patient with a normal transthoracic echocardiogram who had thrombus on his/her transesophageal echocardiogram. Conclusions: Our results suggest that a selective approach may be exercised in the use of transesophageal echocardiography prior to D.C. cardioversion for atrial fibrillation. Patients with an entirely "normal" transthoracic echocardiogram may proceed directly to cardioversion without a precardioversion transesophageal echocardiogram. [source] Management of new onset atrial fibrillation in previously well patients less than 60 years of ageEMERGENCY MEDICINE AUSTRALASIA, Issue 1 2005David McD Taylor Abstract Objective:, This study reviewed the ED management of new onset atrial fibrillation (AF) in previously well patients aged less than 60 years. Methods:, We undertook a retrospective review of ED patients from 1998 to 2002 inclusive. The main outcome measures were approaches to rate or rhythm control and anticoagulation, the use of echocardiography, the value of diagnostic testing and the frequency of hospital admission. Results:, Fifty-two patients were identified. In general, all patients were haemodynamically stable. One patient had mild cardiac failure and one was clinically thyrotoxic. Serum potassium was measured in 51 (98%) patients, magnesium in 23 (44%) and cardiac enzymes in 30 (58%); results were generally unhelpful. Thyroid function tests were carried out in 40 (77%) patients; results were unremarkable except for the clinically thyrotoxic patient. No patient had echocardiography in the ED; however, 6 patients (12%) were later found to have major cardiac abnormalities. Forty-four (85%) patients received a variety of medications; 37 (71%) received an anti-arrhythmic and 24 (46%) an antithrombotic. Overall, 17 (33%) patients received theoretically effective therapy for conversion to sinus rhythm. Twenty-two (42%) patients were admitted to hospital. Conclusions:, This study reveals variation in the management of acute AF in previously well, haemodynamically stable, young patients. Pathology testing was frequently carried out with a low yield. There were high rates of attempts to cardiovert, use of antithrombotics and of admission to hospital. Although cardioversion attempts appeared to be contrary to existing guidelines, decisions may have been based primarily on patient symptoms. Echocardiography should be considered prior to anti-arrhythmic therapy. [source] Dynamic modelling of bacterial cellulose formationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2009Michael Hornung Abstract The interest in cellulose produced by bacteria from surface cultures has increased steadily in recent years because of its potential for use in medicine and cosmetics. Unfortunately, the low yield of this production process has limited the commercial usefulness of bacterial cellulose. The aim of this paper is to show the effect of substrate mass transfer on the growth of the bacteria and on their physiological potential for product formation by means of a dynamic mathematical model. [source] Norbornane Mimics of Distorted , - D -Glucopyranosides , Inhibitors of , - D -Glucopyranosidases?HELVETICA CHIMICA ACTA, Issue 4 2006Stephan Buser Abstract The racemic gluco -configured norbornanes 4 and 16 were prepared and tested as inhibitors of ,- glucosidases. The known alcohol 5 was deprotected to provide the triol 6. Silylation (,,7), monobenzoylation (,,8/9), and oxidation provided the regioisomeric ketones 10 and 11. Reduction of 10 gave the desired endo -alcohol 13, albeit in low yield, while reduction of the isomeric ketone 11 provided mostly the altro -configured endo -alcohol 12. The alcohol 13 was desilylated to 14. Debenzoylation to 15 followed by hydrogenolytic deprotection gave the amino triol 4 that was reductively aminated to the benzylamine 16. The amino triols 4 and 16 proved weak inhibitors of the , -glucosidase from Caldocellum saccharolyticum (4: IC50,=,5.6,mm; 16:IC50,=,3.3,mm) and from sweet,almonds (16:IC50,=,5.5,mm). A comparison of 4 with the manno -configured norbornane 3 shows that 3 is a better inhibitor of snail , -mannosidase than 4 is of ,- glucosidases, in keeping with earlier results suggesting that these , -glycosidases enforce a different conformational itinerary. [source] The Diagnosis of Cardiac Arrhythmias: A Prospective Multi-Center Randomized Study Comparing Mobile Cardiac Outpatient Telemetry Versus Standard Loop Event MonitoringJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2007STEVEN A. ROTHMAN M.D. Introduction: Ambulatory electrocardiographic monitoring systems are frequently used in the outpatient evaluation of symptoms suggestive of a cardiac arrhythmia; however, they have a low yield in the identification of clinically significant but infrequent, brief, and/or intermittently symptomatic arrhythmias. The purpose of this study was to compare the relative value of a mobile cardiac outpatient telemetry system (MCOT) with a patient-activated external looping event monitor (LOOP) for symptoms thought to be due to an arrhythmia. Methods and Results: The study was a 17-center prospective clinical trial with patients randomized to either LOOP or MCOT for up to 30 days. Subjects with symptoms of syncope, presyncope, or severe palpitations who had a nondiagnostic 24-hour Holter monitor were randomized. The primary endpoint was the confirmation or exclusion of a probable arrhythmic cause of their symptoms. A total of 266 patients who completed the monitoring period were analyzed. A diagnosis was made in 88% of MCOT subjects compared with 75% of LOOP subjects (P = 0.008). In a subgroup of patients presenting with syncope or presyncope, a diagnosis was made in 89% of MCOT subjects versus 69% of LOOP subjects (P = 0.008). MCOT was superior in confirming the diagnosis of clinical significant arrhythmias, detecting such events in 55 of 134 patients (41%) compared with 19 of 132 patients (15%) in the LOOP group (P < 0.001). Conclusions: MCOT provided a significantly higher yield than standard cardiac loop recorders in patients with symptoms suggestive of a significant cardiac arrhythmia. [source] Are Routine Arrhythmia Inductions Necessary in Patients with Pectoral Implantable Cardioverter Defibrillators?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2000MICHAEL GLIKSON M.D. Routine Arrhythmia Inductions in Patients with ICDs. Introduction: The value of ventricular arrhythmia inductions as part of routine implantable cardioverter defibrillator (ICD) follow-up in new-generation pectoral ICDs is unknown Methods and Results: We performed a retrospective analysis of a prospectively collected database analyzing data from 153 patients with pectoral ICDs who had routine arrhythmia inductions at predismissal, and 3 months and 1 year after implantation. Routine predismissal ventricular fibrillation (VF) induction yielded important findings in 8.8% of patients, all in patients with implantation defibrillation threshold (DFT) , 15 J or with concomitant pacemaker systems. At 3 months and 1 year, routine VF induction yielded important findings in 5.9% and 3.8% of tested patients, respectively, all in patients who had high DFT on prior testing. Ventricular tachycardia (VT) induction at predismissal, and 3 months and 1 year after implantation resulted in programming change in 37.4%, 28.1%, and 13.8% of tested patients, almost all in patients with inducible VT on baseline electrophysiologic study and clinical episodes since implantation. Conclusion: Although helpful in identifying potentially important ICD malfunctions, routine arrhythmia inductions during the first year after ICD implantation may not be necessary in all cases. VF inductions have a low yield in patients with previously low DFTs who lack concomitant pacemakers. VT inductions have a low yield in patients without baseline Inducible VT and in the absence of clinical events. Definite recommendations regarding patient selection must await larger prospective studies as well as consensus in the medical community about what comprises an acceptable risk justifying avoidance of the costs and inconveniences of routine arrhythmia inductions. [source] Improvements in the production of bacterial synthesized biocellulose nanofibres using different culture methodsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2010Amir Sani Abstract This review summarizes previous work that was done to improve the production of bacterial cellulose nanofibres. Production of biocellulose nanofibres is a subject of interest owing to the wide range of unique properties that makes this product an attractive material for many applications. Bacterial cellulose is a natural nanomaterial that has a native dimension of less than 50 nm in diameter. It is produced in the form of nanofibres, yielding a very pure cellulose product with unique physical properties that distinguish it from plant-derived cellulose. Its high surface-to-volume ratio combined with its unique properties such as poly-functionality, hydrophilicity and biocompatibility makes it a potential material for applications in the biomedical field. The purpose of this review is to summarize the methods that might help in delivering microbial cellulose to the market at a competitive cost. Different feedstocks in addition to different bioreactor systems that have been previously used are reviewed. The main challenge that exists is the low yield of the cellulosic nanofibres, which can be produced in static and agitated cultures. The static culture method has been used for many years. However, the production cost of this nanomaterial in bioreactor systems is less expensive than the static culture method. Biosynthesis in bioreactors will also be less labour intensive when scaled up. This would improve developing intermediate fermentation scale-up so that the conversion to an efficient large-scale fermentation technology will be an easy task. Copyright © 2009 Society of Chemical Industry [source] Synthetic analogs of dioncophylline and michellamines by stille couplingJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2006Abdel-Sattar S. Hamad Elgazwy Dioncophielline and Michellamine Analogs S-5, R-5, S-7, R-7, S,S-8, R,R-8 and R,S-8 were synthesized by using Stille coupling condition (Pd°-mediated cross coupling) proceeds in low yield when using stannanes 1 or 2 with tetrahydroisoquinolinyl bromide 3. The addition of tetrahydroisoquinolinyl iodide 4 instead of 3 significantly improves the efficiency of the coupling and providing a variety of Dioncophielline and Michellamine analogs in moderate yields. [source] Do collisions inside the collision cell play a relevant role in CID-LIFT experiments?,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2007Gloriano Moneti Abstract Collision experiments are a valid approach to characterize the ionic species generated by matrix assisted laser desorption ionization (MALDI). When a time-of-flight analyzer is employed, three different approaches are available for these experiments: the postsource decay (PSD), the LIFT and the MALDI-TOF/TOF. The last two are of particular interest because of the overcoming of the PSD problems related to mass calibration of the product ion spectra. Experiments performed by LIFT on linear or cyclic peptides, in presence or in absence of collision gas in the collision cell, gave evidence of an unexpected behavior: the two spectra were practically superimposable, and in the former case only a few new fragmentation channels were activated with low yield. These results mean that the selected ion exhibits a large amount of internal energy, capable of promoting fragmentation processes in the time window corresponding to the flight time between ion source and the acceleration electrode placed after the collision cell. Experiments performed by varying the plume density show that this internal energy uptake occurs in the expanding plume, through multiple collisions. The LIFT data have been compared with those achieved by collisions of ESI-generated [MH]+ ions of angotensin II performed under ,in-source' conditions and by triple-quadrupole experiments. The obtained results show a strong similarity among the spectra, indicating that the internal energy uptake in a MALDI source is comparable with that of 40-eV ions colliding with Ar in a triple-quadrupole instrument. Copyright © 2006 John Wiley & Sons, Ltd. [source] Xanthene dye functionalized norbornenes for the use in ring opening metathesis polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2007Martina Sandholzer Abstract A convenient synthetic route towards polymerizable fluorescein, dicholorofluorescein, and eosin dyes is presented. Polymerizability was provided by linking 2-norbornene carboxylic acid, 11-bromo-undecyl ester to the dye's carboxylate functionality. Although the monomers bearing dichlorofluorescein and eosin were obtained in high yield, the related fluorescein bearing monomer could only be obtained in low yield. In the latter case, concurring etherification and esterification led to a product mixture of the desired carboxy modified monomer and a double substituted by-product. The dye-monomers were used successfully for the preparation of statistical copolymers with endo,exo -2,3-norbornene dicarboxylic acid dimethylester by ROMP. Absorption and luminescence characteristics and, in particular, the acid/base sensitive behavior of the parent dyes were preserved in the monomers and copolymers. The absorption and emission maxima in THF solution and in the solid state were red shifted in comparison to the aqueous samples of the parent dyes. Dye-copolymers exhibited good film forming properties. Solid state luminescence studies of the copolymers revealed an increasing sensitivity towards NEt3 vapor in the order fluorescein < dichlorofluorescein < eosin bearing copolymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1336,1348, 2007 [source] Synthesis and polymerization of (E)- p -[(p -methoxyphenyl)-2-ethenyl]phenylacetylene with Ziegler,Natta, rhodium, and palladium complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2005J. Gonzalo Rodríguez Abstract The synthesis and polymerization of (E)- p -[(p -methoxyphenyl)-2-ethenyl]phenylacetylene was carried out with a homogeneous vanadium acetylacetonate/aluminum triethyl catalyst system, a bis(rhodium chloride cycloocta-1,5-diene) complex, and a palladium/trimethylsilyl complex. In all cases, the main fraction was a polymer with a stereoregular structure. The polymerization with the vanadium catalyst gave a polymer fraction in a low yield. The polymerization of (E)- p -[(p -methoxyphenyl)-2-ethenyl]phenylacetylene with the soluble rhodium complex gave a polymer in a high yield. The soluble palladium/chlorotrimethylsilane complex gave a polymer in a good yield. On the basis of the spectroscopic data, the poly{(E)- p -[(p -methoxyphenyl)-2-ethenyl]phenylacetylene)} obtained, in all cases, showed a cis,transoidal stereoregular structure. The molecular mass of poly{(E)- p -[(p -methoxyphenyl)-2-ethenyl]phenylacetylene)} was determined by the matrix-assisted laser desorption/ionization time-of-flight technique. The kinetics of the reaction were analyzed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6438,6444, 2005 [source] The weed community affects yield and quality of soybean (Glycine max (L.) Merr.)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2008David J Gibson Abstract BACKGROUND: The relationship between the weed community and soybean (Glycine max (L.) Merr.) seed yield and quality was assessed in two experiments in Illinois, USA. In one field different proportions of target weeds (Ambrosia trifida L., Amaranthus rudis J. Sauer, and Setaria faberi F. Herrm) were sown into experimental plots, and the other field was naturally infested with these and other weeds. The composition of the weed communities in both fields was compared to soybean yield, biomass, canopy cover and quality (% protein, oil, relative water content, and seed weight) using non-metric dimensional scaling ordination. RESULTS: In the experimentally sown plots, low yield and low quality soybeans were harvested from plots dominated by the target weeds, particularly A. trifida, and a suite of subordinate volunteers. In the naturally infested field, highest soybean protein was associated with S. faberi early in the season and Ambrosia artemisiifolia and Ipomea hederacea later in the season, and low amounts of A. rudis throughout the growing season. CONCLUSION: Similar results from the two experiments indicate that soybean seed yield and quality are affected by the composition of the weed community. Producers need to manage the weed community to optimize seed quality. Copyright © 2007 Society of Chemical Industry [source] Experience of Severe Acute Respiratory Syndrome in Singapore: Importation of Cases, and Defense Strategies at the AirportJOURNAL OF TRAVEL MEDICINE, Issue 5 2003Annelies Wilder-Smith Background The importation of SARS was responsible for the outbreaks in Singapore, Hong Kong, Vietnam and Canada at a time when this new disease had not been identified. We report the incidence and impact of cases of SARS imported to Singapore between 25 February and 31 May 2003, and describe national measures to prevent further importation. Methods Information on imported cases of SARS and measures taken at entry points to Singapore was retrieved from the Ministry of Health and the Civil Aviation Authority of Singapore. Results Of the 6 imported cases, which all occurred before screening measures were implemented at the airport, only the first resulted in extensive secondary transmission. Of 442,973 air passengers screened after measures were implemented, 136 were sent to a designated hospital for further SARS screening; none was diagnosed as having SARS. Conclusions The SARS outbreak in Singapore can be traced to the first imported case. The absence of transmission from the other imported cases was probably a result of relatively prompt identification and isolation of cases, together with a low potential for transmission. New imported SARS cases therefore need not lead to major outbreaks if systems are in place to identify and isolate them early. Screening at entry points is costly, has a low yield and is not sufficient in itself, but may be justified in light of the major economic, social and international impact which even a single imported SARS case may have. [source] Structural elucidation by 1D and 2D NMR of three isomers of a carotenoid lysophosphocholine and its synthetic precursorsMAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2004Bente Jeanette Foss Abstract A carotenoic acid was used to obtain a long-chain unsaturated lysophosphocholine. The carotenoid lysophosphocholine was synthesized by two methods. The first method resulted in mixtures of regioisomers for each step in the synthetic route. Homo- and heteronuclear 1D and 2D NMR methods were employed to elucidate the structures of the individual isomers and their intermediates. The pure regioisomer [1-(,-apo-8, -carotenoyl)-2-lyso- glycero -3-phosphocholine] was obtained by a second method, but in low yield. The 1D 1H NMR subtraction spectrum of the mixture and the pure regioisomer was used to interpret the 1H shifts of the unsaturated acyl moieties. The 1H and 13C signals of the acyl chain show characteristic shifts depending on the positions of the choline and the acyl group attached to the glycerol backbone. Therefore, the unsaturated acyl chain signals have diagnostic values for the identification of isomers of unsaturated (lyso)phosphocholines. Chemical shifts and indirect coupling constants are reported for each of the major components of the mixtures. The methods used were 1D (1H, 13C and 31P) and 2D (H,H-COSY, HMBC, HSQC and HETCOR) NMR. Copyright © 2004 John Wiley & Sons, Ltd. [source] Deciphering regulatory mechanisms for secondary metabolite production in the myxobacterium Sorangium cellulosum So ce56MOLECULAR MICROBIOLOGY, Issue 6 2007Shwan Rachid Summary Sorangium cellulosum strains produce approximately 50% of the biologically active secondary metabolites known from myxobacteria. These metabolites include several compounds of biotechnological importance such as the epothilones and chivosazols, which, respectively, stabilize the tubulin and actin skeletons of eukaryotic cells. S. cellulosum is characterized by its slow growth rate, and natural products are typically produced in low yield. In this study, biomagnetic bead separation of promoter-binding proteins and subsequent inactivation experiments were employed to identify the chivosazol regulator, ChiR, as a positive regulator of chivosazol biosynthesis in the genome-sequenced strain So ce56. Overexpression of chiR under the control of T7A1 promoter in a merodiploid mutant resulted in fivefold overproduction of chivosazol in a kinetic shake flask experiment, and 2.5-fold overproduction by fermentation. Using quantitative reverse transcription PCR and gel shift experiments employing heterologously expressed ChiR, we have shown that transcription of the chivosazol biosynthetic genes (chiA,chiF) is directly controlled by this protein. In addition, we have demonstrated that ChiR serves as a pleiotropic regulator in S. cellulosum, because mutant strains lack the ability to develop into regular fruiting bodies. [source] Yield of Terminal Duct Lobule Units in Normal Breast Stereotactic Core Biopsy Specimens: Implications for Biomarker StudiesTHE BREAST JOURNAL, Issue 4 2000Samina Mansoor MD Abstract: The purpose of this study was to assess the potential value of large-needle core biopsies of normal breast tissue for immunohistochemical studies of epithelial risk assessment. A retrospective analysis was performed to determine the yield of nonatrophic terminal duct lobule units (TDLUs) in 11-gauge vacuum-assisted core biopsies of normal adjacent breast tissue which were included in routine stereotactic core biopsies of benign lesions. Fifty-one patients had a median of two normal tissue cores (range 1,7); 82% of the patients had two or more normal tissue cores; 47% had three or more normal tissue cores. Nonatrophic TDLUs were present in only 47% of patients and in 31% (42 of 137) of all cores. Patients with heterogeneous or dense normal mammographic parenchyma at the site of the biopsy were more likely to have nonatrophic TDLUs, 45% (20 of 44), than patients with fatty normal mammographic parenchyma at the biopsy site, 0% (0 of 7), p = 0.007. Seventy percent (7 of 10) of postmenopausal women on hormone replacement therapy had nonatrophic TDLUs as compared to 41% (11 of 27) of premenopausal and postmenopausal women not on hormones (p = not significant). Eleven-gauge vacuum-assisted core biopsies of normal breast tissue have a low yield of nonatrophic TDLUs suitable for histochemical studies of epithelial risk assessment. [source] Is Hospital Admission and Observation Required after a Normal Abdominal Computed Tomography Scan in Children with Blunt Abdominal Trauma?ACADEMIC EMERGENCY MEDICINE, Issue 10 2008Smita Awasthi MD Abstract Objectives:, The objective was to determine if hospital admission of children with blunt abdominal trauma for observation of possible intraabdominal injury (IAI) is necessary after a normal abdominal computed tomography (CT) scan in the emergency department (ED). Methods:, The authors conducted a prospective observational cohort study of children less than 18 years of age with blunt abdominal trauma who underwent an abdominal CT scan in the ED. Abdominal CT scans were obtained with intravenous contrast but no oral contrast. The decision to hospitalize the patient was made by the attending emergency physician (EP) with the trauma or pediatric surgery teams. An abnormal abdominal CT scan was defined by the presence of any visualized IAI or findings suggestive of possible IAI (e.g., intraperitoneal fluid without solid organ injury). Patients were followed to determine if IAI was later diagnosed and the need for acute therapeutic intervention if IAI was present. Results:, A total of 1,295 patients underwent abdominal CT, and 1,085 (84%) patients had normal abdominal CT scans in the ED and make up the study population. Seven-hundred thirty-seven (68%) were hospitalized, and 348 were discharged to home. None of the 348 patients discharged home and 2 of the 737 hospitalized patients were identified with an IAI after a normal initial abdominal CT. The IAIs in patients with normal initial CT scans included a 10-year-old with a mesenteric hematoma and serosal tear at laparotomy and a 10-year-old with a perinephric hematoma on repeat CT. Neither underwent specific therapy. The negative predictive value (NPV) of a normal abdominal CT scan for IAI was 99.8% (95% confidence interval [CI] = 99.3% to 100%). Conclusions:, Children with blunt abdominal trauma and a normal abdominal CT scan in the ED are at very low risk of having a subsequently diagnosed IAI and are very unlikely to require a therapeutic intervention. Hospitalization of children for evaluation of possible undiagnosed IAI after a normal abdominal CT scan has a low yield and is generally unnecessary. [source] Photoallergic contact dermatitis is uncommonBRITISH JOURNAL OF DERMATOLOGY, Issue 4 2001A. Darvay Background Despite the enormous increase in sunscreen use, allergic contact (AC) and photoallergic (PA) reactions to ultraviolet (UV) filters are considered rare. Objectives To analyse the data from 2715 patients who underwent photopatch testing at St John's Institute of Dermatology during the period 1983,98. Methods A retrospective analysis of all positive photopatch test episodes was undertaken with the results retrieved from the environmental dermatology database and further verified with the original archived patch test documentation for each individual patient. Results In 111 patients with positive reactions (4·1%), there were 155 AC or PA reactions to allergens in the photopatch test series. Eighty PA reactions were observed in 62 (2·3%) patients (32 men and 30 women, age range 28,75 years), with UV filters accounting for 52 positive reactions (65%), drugs 16 (20%), musk ambrette 11 (14%) and the antiseptic trichlorocarbanilide one (1%). The most common UV filter photoallergen was benzophenone-3 with 14 positive results, followed by benzophenone-10 (n = 9), isopropyl dibenzoylmethane (n = 6), p -aminobenzoic acid (PABA) (n = 5), octyl dimethyl PABA (n = 5), butyl methoxydibenzoylmethane (n = 4), isoamyl methoxycinnamate (n = 2), ethyl methoxycinnamate (n = 2), octyl methoxycinnamate (n = 2), amyl dimethyl PABA (n = 2) and phenylbenzimidazole sulphonic acid (n = 1). A similar number of AC reactions to UV filters was detected in this study. Thus 49 patients (1·8%) had a total of 75 reactions: 51 due to UV filters and 24 as a result of exposure to fragrances and therapeutic agents. Benzophenone-10 accounted for 13 AC reactions and benzophenone-3 for eight reactions. Twenty-two patients had a PA reaction alone, whereas 19 patients had chronic actinic dermatitis and 15 patients polymorphic light eruption (PLE) in addition. Thus, 34 of the 62 patients (55%) had a preceding underlying photodermatosis. Conclusions These results show a low yield of positive photopatch tests. Thus, despite the large increase in the use of UV filters over the last decade, the development of PA reactions remains rare. Furthermore, most of the common UV filter photoallergens identified in this study, including PABA, amyl dimethyl PABA and benzophenone-10, are now rarely used in sunscreen manufacture, while isopropyl dibenzoylmethane was voluntarily removed from the market in 1993. Currently, benzophenone-3 is the commonest contact photoallergen still in widespread use. In contrast, the UVB filter octyl methoxycinnamate, used in a number of sunscreens, produced only two positive PA reactions in 12 years of testing. Nevertheless, although these reactions are extremely rare, patients with photodermatoses such as PLE and chronic actinic dermatitis do represent a group of patients at increased risk of developing photoallergy. Further photopatch test series should be regularly reviewed and updated, as the relevance of individual photoallergens changes over time. Currently, there is no evidence that PA reactions represent a common clinical problem. [source] Development of an Industrial Multi-Injection Microreactor for Fast and Exothermic Reactions , Part IICHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2008D. M. Roberge Abstract A Grignard reaction performed in a microreactor is presented. The reaction is of type A (highly exothermic and very rapid) and has a low yield which is attributed to a hot spot formed in the mixing zone of the reactor. The reaction yield could be significantly increased by applying the multi-injection principle, leading to better thermal control in the microreactor. Nevertheless, the microreactor plays a major role in reducing the magnitude of the hot spot. Knowing this, it was possible to design and construct an industrial microreactor with significant advantages such as modularity, high flow rate operation, and low investment expenditure (pumps and flow controller minimization). [source] ,-Diketiminate-Stabilized Magnesium(I) Dimers and Magnesium(II) Hydride Complexes: Synthesis, Characterization, Adduct Formation, and Reactivity StudiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2010Simon Abstract The preparation and characterization of a series of magnesium(II) iodide complexes incorporating ,-diketiminate ligands of varying steric bulk and denticity, namely, [(ArNCMe)2CH], (Ar=phenyl, (PhNacnac), mesityl (MesNacnac), or 2,6-diisopropylphenyl (Dipp, DippNacnac)), [(DippNCtBu)2CH], (tBuNacnac), and [(DippNCMe)(Me2NCH2CH2NCMe)CH], (DmedaNacnac) are reported. The complexes [(PhNacnac)MgI(OEt2)], [(MesNacnac)MgI(OEt2)], [(DmedaNacnac)MgI(OEt2)], [(MesNacnac)MgI(thf)], [(DippNacnac)MgI(thf)], [(tBuNacnac)MgI], and [(tBuNacnac)MgI(DMAP)] (DMAP=4-dimethylaminopyridine) were shown to be monomeric by X-ray crystallography. In addition, the related ,-diketiminato beryllium and calcium iodide complexes, [(MesNacnac)BeI] and [{(DippNacnac)CaI(OEt2)}2] were prepared and crystallographically characterized. The reductions of all metal(II) iodide complexes by using various reagents were attempted. In two cases these reactions led to the magnesium(I) dimers, [(MesNacnac)MgMg(MesNacnac)] and [(tBuNacnac)MgMg(tBuNacnac)]. The reduction of a 1:1 mixture of [(DippNacnac)MgI(OEt2)] and [(MesNacnac)MgI(OEt2)] with potassium gave a low yield of the crystallographically characterized complex [(DippNacnac)Mg(,-H)(,-I)Mg(MesNacnac)]. All attempts to form beryllium(I) or calcium(I) dimers by reductions of [(MesNacnac)BeI], [{(DippNacnac)CaI(OEt2)}2], or [{(tBuNacnac)CaI(thf)}2] have so far been unsuccessful. The further reactivity of the magnesium(I) complexes [(MesNacnac)MgMg(MesNacnac)] and [(tBuNacnac)MgMg(tBuNacnac)] towards a variety of Lewis bases and unsaturated organic substrates was explored. These studies led to the complexes [(MesNacnac)Mg(L)Mg(L)(MesNacnac)] (L=THF or DMAP), [(MesNacnac)Mg(,-AdN6Ad)Mg(MesNacnac)] (Ad=1-adamantyl), [(tBuNacnac)Mg(,-AdN6Ad)Mg(tBuNacnac)], and [(MesNacnac)Mg(,- tBu2N2C2O2)Mg(MesNacnac)] and revealed that, in general, the reactivity of the magnesium(I) dimers is inversely proportional to their steric bulk. The preparation and characterization of [(tBuNacnac)Mg(,-H)2Mg(tBuNacnac)] has shown the compound to have different structural and physical properties to [(tBuNacnac)MgMg(tBuNacnac)]. Treatment of the former with DMAP has given [(tBuNacnac)Mg(H)(DMAP)], the X-ray crystal structure of which disclosed it to be the first structurally authenticated terminal magnesium hydride complex. Although attempts to prepare [(MesNacnac)Mg(,-H)2Mg(MesNacnac)] were not successful, a neutron diffraction study of the corresponding magnesium(I) complex, [(MesNacnac)MgMg(MesNacnac)] confirmed that the compound is devoid of hydride ligands. [source] Six-membered cyclic sulfites derived from glucofuranose and 1,2,4-butanetriol,CHIRALITY, Issue 9 2001Katarzyna Borsuk Abstract Six-membered cyclic sulfites derived from glucofuranose derivatives 5, 6 and from 1- O-tert -butyldimethylsilil-1,2,4-butanetriol 12 were synthesized and separated into pure diastereomers which were in turn subjected to the sequence of reactions leading to the introduction of the terminal vinyl ether fragment. Reactivity and applicability of cyclic sulfites as intermediates in [2+2]cycloaddition of chlorosulfonyl isocyanate (CSI) to vinyl ethers were studied. The cycloaddition to vinyl ethers 19 and 20 proceeded in low yield and low asymmetric induction, in the case of the former, and moderate yield and pronounced asymmetric induction, in the case of the latter. The 1H-NMR spectra of sulfites 13,16 reveal a preference of the sulfite oxygen atom for the axial position. Thus, well-defined conformation in solution for compounds 13 and 15 and a mixture of the two possible chair forms for sulfites 14 and 16 could be assigned. The stretching frequency of the S,O bond in stable conformation with an axial sulfite oxygen occurs in the range 1,160,1,210 cm,1, whereas conformationally mobile sulfites exhibit corresponding absorption above 1,220 cm,1. The absolute configuration assignments of sulfites 7, 8, 15, 16 and 25,28 were done empirically based on the combined analysis of the NMR, IR, X-ray, and dichroic data. It was demonstrated that the sign of the Cotton effect around 194 nm correlated with the absolute stereochemistry at the sulfur atom in a sulfite chromophore. Chirality 13:533,540, 2001. © 2001 Wiley-Liss, Inc. 2001. [source] Inter general practice variability in use of referral guidelines for colorectal cancerCOLORECTAL DISEASE, Issue 8 2007S. K. P. John Abstract Objective, The Two-Week Wait (TWW) referral system for suspected colorectal cancers has a low yield. To examine this, we assessed the referral pattern of general practices within four primary care trusts and looked at the variability of yield of colorectal cancer amongst all TWW referrals and assessed the reasons for variability. Method, A prospectively collected database of all colorectal cancers was examined for new cases diagnosed in the 12 months from April 1st 2004. Patients were cross-referenced via general practitioner (GP) codes to identify the referral origin. Reasons for the variability in referral patterns from each general practice were assessed in relation to TWW referrals, population demographics and through postal questionnaire of GPs. Results, A total of 175 patients diagnosed with colorectal cancer were referred from 49 general practices. Whilst there was a positive correlation between the number of TWW referrals and colorectal cancer per 1000-practice population (P = 0.001; Spearman correlation coefficient rs=0.447, two-tailed), there was a big discrepancy between referrals and cancer diagnosed in many general practices. Twenty-six general practices (53%) had no colorectal cancer diagnosed via the TWW route and these practices had significantly lower utilization of the TWW referral pathway. In the postal survey, 22% of GPs were unaware of TWW clinics or colorectal cancer referral guidelines and only 8% of GPs knew the number of referral criteria. Conclusion, This study demonstrates wide variability within primary care, in the appropriate use of colorectal cancer referral guidelines. General practices should be targeted for education. [source] Photochemical Reactivity of 2-Azido-1,3-thiazole and 2-Azido-1,3-benzothiazole: A Procedure for the Aziridination of Enol EthersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2009Maurizio D'Auria Abstract Direct irradiation of a mixture of the azido,tetrazole tautomers of 2-azido-1,3-thiazole and 2-azido-1,3-benzothiazole in toluene solution gives products arising from the intermediate nitrene, which in turn undergoes ring opening in the case of 2-azido-1,3-thiazole to give a polymer, and dimerization in the case of 2-azido-1,3-benzothiazole to give [1,3]benzothiazolo[2,,3,:3,4][1,2,4,5]tetraazino[6,1b][1,3]benzothiazolein low yields. When irradiation is performed in the presence of methyl acrylate or various enol ethers, aziridination of the double bond is observed, with good yields in the case of enol ethers. Among these, 1-(6-methyl-3,4-dihydro-2H -pyran-2-yl)ethanone undergoes aziridination with complete diastereoselectivity to give the (1RS,3RS,6SR) diastereomer.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Enhancing Security Value by Ownership Restrictions: Evidence from a Natural ExperimentFINANCIAL MANAGEMENT, Issue 4 2005Amar Gande We present new evidence from a natural experiment to show circumstances in which ownership restrictions can enhance value. Our evidence is based on multiple restricted bond issues by an emerging market issuer at 150 basis points lower than comparable bonds, resulting in a billion dollars saving. This is intriguing: how can an emerging market issuer with junk bond ratings obtain such low yields? We argue ownership restrictions enhance value since they enable an issuer to precommit to renegotiate efficiently with a favored clientele in the potential default states, thereby circumventing deadweight costs of prolonged negotiations, particularly when the restricted clientele also values the underlying collateral higher than other investors. Ownership restrictions can also result in a transfer of value from holders of unrestricted bonds to holders of restricted bonds because of implicit seniority of the latter. We empirically test and find support for both value enhancement and value transfer and show robustness to several alternative explanations. Our evidence suggests that firms can benefit from designing securities with ownership restrictions, by offering new securities exclusively to investors who value them the most. [source] Impact of the timing of stocking on growth and allometric index in aquaculture-based fisheriesFISHERIES MANAGEMENT & ECOLOGY, Issue 2 2004A. L. Ibáńez Abstract The impact of tilapia stocking on fisheries production in Lake Metztitlán was determined through progression analysis of modes obtained from (Gaussian) kernel density estimators (KDEs) of size frequency distributions of juvenile tilapia stocked after a period of total desiccation. The relationship between the allometric index of four cohorts and water temperature and variation in the volume of the basin was analysed. The use of KDEs was found to be a useful technique for the recognition and progression analysis of modes. The reasons for the low yields from the tilapia fishery of Lake Metztitlán are poor growth rate, low water temperature, which is manifest in low allometric indices, and the use of small mesh size nets. Yields can be sustained by improving fishery management; otherwise it is necessary to continue stocking. [source] Phosphono-substituted isoindolines and indoles from 2,3- and 2,4-benzoxazin-1-onesHETEROATOM CHEMISTRY, Issue 1 2004Wafaa M. Abdou Reactions of 2,3-benzoxazinone 1 and 2,4-benzoxazinone 2, with trialkyl phosphites 3a,c provide access to new phosphono-substituted isoindolines 6a,f and indoles 19a,e, respectively. Phosphono-substituted 2,3-benzoxazines 5a,c were also obtained in the first reaction. Bisisoindolinylidene (7) was, however, isolated in low yields when 1 was heated with triethyl or triisopropyl phosphite at 100deg;C whereas at 170deg;C 7 was obtained as the major product (,53%). On the other hand, the reaction of 1 or 2 with dialkyl phosphonates 4a,c proceeded in the presence of aqueous solution of NaOH (5%) to give the respective alkylated product 14a,c or 20a,c. © 2003 Wiley Periodicals, Inc. 15:77,84, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.10216 [source] The use of SST and SOI anomalies as indicators of crop yield variabilityINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2009Maria I. Travasso Abstract Interannual climate variability accounts for most of the observed crop yield fluctuations in the main agricultural region of Argentina. Moreover, in this region climatic variations are related to sea surface temperatures (SST) and the Southern Oscillation Index (SOI). In the present study, we aimed to obtain indicators of crop yield variability based on these drivers. For this purpose, monthly anomalies corresponding to SSTs from the Equatorial Pacific (SSTN3) and South Atlantic (SSTSA) Oceans and the SOI were related to maize, sunflower and soybean grain yield anomalies. Historical data (1923,2000 for maize, 1934,2000 for sunflower and 1969,2000 for soybean) were used to obtain grain yield anomalies at the county level after removing technology trends by smoothing techniques. By means of correlation analysis, we obtained the counties presenting significant association (p < 0.05) between monthly SST/SOI anomalies and yield anomalies, for the period 1950,1997. Those indicators showing spatial consistency were classified in percentiles, and the values corresponding to the upper and lower terciles showed to be useful to discriminate between positive and negative yield anomalies (high and low yields). In general, SOI for maize and SSTSA for soybean and sunflower were the best indicators of crop yield variability. SOI corresponding to September and May were useful in counties contributing to 71% of maize production. SSTa_SA (June) was the best for soybean in the main producing region, which includes 72% of the total production. SSTa_SA (March) could be useful for sunflower in the northern part of the region, which accounts for 27% of the regional production. Copyright © 2008 Royal Meteorological Society [source] Palladium(II) Complexes of C2 -Bridged Chiral Diphosphines: Application to Enantioselective Carbonyl-Ene ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 8 2010He-Kuan Luo Abstract (11bR,11,bR)-4,4,-(1,2-Phenylene)bis[4,5-dihydro-3H -dinaphtho[2,1- c:1,,2,- e]phosphepin] [abbreviated as (R)-BINAPHANE], (3R,3,R,4S,4,S,11bS,11,bS)-4,4,-bis(1,1-dimethylethyl)-4,4,,5,5,-tetrahydro-3,3,-bi-3H -dinaphtho[2,1- c:1,,2,- e]phosphepin [(S)-BINAPINE], (1S,1,S,2R,2,R)-1,1,-bis(1,1-dimethylethyl)-2,2,-biphospholane [(S,S,R,R)-TANGPHOS] and (2R,2,R,5R,5,R)-1,1,-(1,2-phenylene)bis[2,5-bis(1-methylethyl)phospholane] [(R,R) -i- Pr-DUPHOS] are C2 -bridged chiral diphosphines that form stable complexes with palladium(II) and platinum(II) containing a five-membered chelate ring. The Pd(II)-BINAPHANE catalyst displayed good to excellent enantioselectivities with ee values as high as 99.0% albeit in low yields for the carbonyl-ene reaction between phenylglyoxal and alkenes. Its Pt(II) counterpart afforded improved yields while retaining satisfactory enantioselectivity. For the carbonyl-ene reaction between ethyl trifluoropyruvate and alkenes, the Pd(II)-BINAPHANE catalyst afforded both good yields and extremely high enantioselectivities with ees as high as 99.6%. A comparative study on the Pd(II) catalysts of the four C2 -bridged chiral diphosphines revealed that Pd(II)-BINAPHANE afforded the best enantioselectivity. The ee values derived from Pd(II)-BINAPHANE are much higher than those derived from the other three Pd(II) catalysts. A comparison of the catalyst structures shows that the Pd(II)-BINAPHANE catalyst is the only one that has two bulky (R)-binaphthyl groups close to the reaction site. Hence it creates a deep chiral space that can efficiently control the reaction behavior in the carbonyl-ene reactions resulting in excellent enantioselectivity. [source] Cyclic Enones as Substrates in the Morita,Baylis,Hillman Reaction: Surfactant Interactions, Scope and Scalability with an Emphasis on FormaldehydeADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Brett Abstract Traditionally, cyclic enones and formalin are reactants notorious for displaying problematic behaviour (i.e., poor solubility and low yields) under Morita,Baylis,Hillman (MBH) reaction conditions. The body of research presented herein focuses on the use of surfactants in water as a solvent medium that offers a resolution to many of the issues associated with the MBH reaction. Reaction scope, scalability and small angle X-ray scattering have been studied to assist with the understanding of the reaction mechanism and industrial application. A comparison against known literature methods for reaction scale-up is also discussed. [source] | |||||||||||||||||||||||||||||||||||||