bluuebunny/crossref_metadata_2025 huggingface dataset:
TLR4 Signaling via MyD88 and TRIF Differentially Shape the CD4+ T Cell Response to Porphyromonas gingivalis Hemagglutinin B
Authors: Gaddis Dalia E. , Michalek Suzanne M. , Katz Jannet
Published: April 2011

Recombinant hemagglutinin B (rHagB), a virulence factor of the periodontal pathogen Porphyromonas gingivalis, has been shown to induce protective immunity against bacterial infection. Furthermore, we have demonstrated that rHagB is a TLR4 agonist for dendritic cells. However, it is not known how rHagB dendritic cell stimulation affects the activation and differentiation of T cells. Therefore, we undertook the present study to examine the role of TLR4 signaling in shaping the CD4+ T cell response following immunization of mice with rHagB. Immunization with this Ag resulted in the induction of specific CD4+ T cells and Ab responses. In TLR4−/− and MyD88−/− but not Toll/IL-1R domain-containing adapter inducing IFN-β–deficient (TRIFLps2) mice, there was an increase in the Th2 CD4+ T cell subset, a decrease in the Th1 subset, and higher serum IgG1/IgG2 levels of HagB-specific Abs compared with those in wild-type mice. These finding were accompanied by increased GATA-3 and Foxp3 expression and a decrease in the activation of CD4+ T cells isolated from TLR4−/− and MyD88−/− mice. Interestingly, TLR4−/− CD4+ T cells showed an increase in IL-2/STAT5 signaling. Whereas TRIF deficiency had minimal effects on the CD4+ T cell response, it resulted in increased IFN-γ and IL-17 production by memory CD4+ T cells. To our knowledge, these results demonstrate for the first time that TLR4 signaling, via the downstream MyD88 and TRIF molecules, exerts a differential regulation on the CD4+ T cell response to HagB Ag. The gained insight from the present work will aid in designing better therapeutic strategies against P. gingivalis infection.
HLA-A*7401–Mediated Control of HIV Viremia Is Independent of Its Linkage Disequilibrium with HLA-B*5703
Authors: Matthews Philippa C. , Adland Emily , Listgarten Jennifer , Leslie Alasdair , Mkhwanazi Nompumelelo , Carlson Jonathan M. , Harndahl Mikkel , Stryhn Anette , Payne Rebecca P. , Ogwu Anthony , Huang Kuan-Hsiang Gary , Frater John , Paioni Paolo , Kloverpris Henrik , Jooste Pieter , Goedhals Dominique , van Vuuren Cloete , Steyn Dewald , Riddell Lynn , Chen Fabian , Luzzi Graz , Balachandran Thambiah , Ndung’u Thumbi , Buus Søren , Carrington Mary , Shapiro Roger , Heckerman David , Goulder Philip J. R.
Published: April 2011

The potential contribution of HLA-A alleles to viremic control in chronic HIV type 1 (HIV-1) infection has been relatively understudied compared with HLA-B. In these studies, we show that HLA-A*7401 is associated with favorable viremic control in extended southern African cohorts of >2100 C-clade–infected subjects. We present evidence that HLA-A*7401 operates an effect that is independent of HLA-B*5703, with which it is in linkage disequilibrium in some populations, to mediate lowered viremia. We describe a novel statistical approach to detecting additive effects between class I alleles in control of HIV-1 disease, highlighting improved viremic control in subjects with HLA-A*7401 combined with HLA-B*57. In common with HLA-B alleles that are associated with effective control of viremia, HLA-A*7401 presents highly targeted epitopes in several proteins, including Gag, Pol, Rev, and Nef, of which the Gag epitopes appear immunodominant. We identify eight novel putative HLA-A*7401–restricted epitopes, of which three have been defined to the optimal epitope. In common with HLA-B alleles linked with slow progression, viremic control through an HLA-A*7401–restricted response appears to be associated with the selection of escape mutants within Gag epitopes that reduce viral replicative capacity. These studies highlight the potentially important contribution of an HLA-A allele to immune control of HIV infection, which may have been concealed by a stronger effect mediated by an HLA-B allele with which it is in linkage disequilibrium. In addition, these studies identify a factor contributing to different HIV disease outcomes in individuals expressing HLA-B*5703.
Colonic Eosinophilic Inflammation in Experimental Colitis Is Mediated by Ly6Chigh CCR2+ Inflammatory Monocyte/Macrophage-Derived CCL11
Authors: Waddell Amanda , Ahrens Richard , Steinbrecher Kris , Donovan Burke , Rothenberg Marc E. , Munitz Ariel , Hogan Simon P.
Published: April 2011

Recent genome-wide association studies of pediatric inflammatory bowel disease have implicated the 17q12 loci, which contains the eosinophil-specific chemokine gene CCL11, with early-onset inflammatory bowel disease susceptibility. In the current study, we employed a murine model of experimental colitis to define the molecular pathways that regulate CCL11 expression in the chronic intestinal inflammation and pathophysiology of experimental colitis. Bone marrow chimera experiments showed that hematopoietic cell-derived CCL11 is sufficient for CCL11-mediated colonic eosinophilic inflammation. We show that dextran sodium sulfate (DSS) treatment promotes the recruitment of F4/80+CD11b+CCR2+Ly6Chigh inflammatory monocytes into the colon. F4/80+CD11b+CCR2+Ly6Chigh monocytes express CCL11, and their recruitment positively correlated with colonic eosinophilic inflammation. Phenotypic analysis of purified Ly6Chigh intestinal inflammatory macrophages revealed that these cells express both M1- and M2-associated genes, including Il6, Ccl4, Cxcl2, Arg1, Chi3l3, Ccl11, and Il10, respectively. Attenuation of DSS-induced F4/80+CD11b+CCR2+Ly6Chigh monocyte recruitment to the colon in CCR2−/− mice was associated with decreased colonic CCL11 expression, eosinophilic inflammation, and DSS-induced histopathology. These studies identify a mechanism for DSS-induced colonic eosinophilia mediated by Ly6ChighCCR2+ inflammatory monocyte/macrophage-derived CCL11.
Crowe Type I and II Ddh Managed by Large Diameter Metal-on-Metal Total Hip Arthroplasty
Authors: Yalcin Nadir , Kilicarslan Kasim , Cicek Hakan , Kayaalp Cetin , Yildirim Hasan
Published: April 2011

Large bearing metal-on-metal (MOM) total hip arthroplasty (THA) may offer advantages relating to stability and range of motion in patients with Crowe Type I and II developmental dysplasia of the hip (DDH). The purpose of this study was to provide an analysis of the clinical and radiological results of MOM THA in this context and compare the results with a cohort of patients treated with metal-on-polyethylene (MOP) bearing surfaces.

75 hips in 65 patients were treated with cementless MOM THA using large femoral heads (36–56 mm). The mean age of the patients was 47.4 years (29 to 59) and 54 were female. A group of 47 hips (41 patients) treated with conventional THA (screwed cup-polyethylene insert-28mm head) was used for comparison. The study group was followed up for a mean of 62.1 months (32 to 76). No difference was found between the two groups in relation to improvement in Harris hip score (HHS) (43.1 to 90.3 points in the study group, 42.6 to 89.5 points in the control group, p>0.05). Although the preoperative range of motion in all planes were similar in both groups, the large head group demonstrated greater motion in all planes postoperatively, which was significant (all p=0.001). Additionally, there was a significant difference between groups in relation to the necessity for acetabular structural graft (8% and 31.9%, respectively; p=0.001). No major complications or adverse reactions to metal debris (ARMD) were observed in the study group.

The results of large head MOM THA in young and active patients with DDH are similar to conventional THA at early follow-up, but the former offers the advantages of secure acetabular fixation without screws, greater range of motion, and lower risk of dislocation.
Clinical Outcomes of Surgically Managed Ectopic Ureters in 33 DogsS
Authors: Ho Louisa K. , Troy Gregory C. , Waldron Don R.
Published: April 2011

Factors that predict postoperative continence and incontinence were evaluated in 33 female dogs with surgically corrected ectopic ureters. The current study found that intramural or extramural, left- or right-sided, and unilateral or bilateral ectopic ureters were not significant factors influencing postoperative incontinence in affected dogs. The presence of either hydroureter or urinary tract infection was also not significantly associated with postoperative incontinence. Dogs with ectopic ureters that were incontinent postsurgically tended to remain unresolved.
DIC and Granulomatous Vasculitis in a Dog with Disseminated Histoplasmosis
Authors: Gilor Chen , Ridgway Marcella D. , Singh Kuldeep
Published: April 2011

Disseminated histoplasmosis and disseminated intravascular coagulopathy were diagnosed in a 7 mo old, female spayed mixed-breed dog. The dog improved transiently with supportive care, but deteriorated shortly after initiation of antifungal therapy. The dog was subsequently euthanized. At necropsy, marked granulomatous vasculitis was identified in all affected organs. The tunicae and laminae of the arteries and arterioles were obscured by epithelioid macrophages and multinucleated giant cells admixed with necrotic material. Intracytoplasmic yeast were present within some of these macrophages. To the authors' knowledge, this is the first reported case of granulomatous vasculitis associated with Histoplasma capsulatum in a dog.
Segmental Jejunal Entrapment, Volvulus, and Strangulation Secondary to Intra-abdominal Adhesions in a Dog
Authors: Di Cicco Michael F. , Bennett R. Avery , Ragetly Chantal , Sippel Kate M.
Published: April 2011

A 4 yr old, castrated male dachshund was presented for lethargy, restlessness, a “hunched” posture, and a painful abdomen. A gastric foreign body had been surgically removed 24 mo previously. Exploratory celiotomy revealed a devitalized segment of jejunum with twisted mesentery. Several adhesions and fibrous bands were present within the abdomen, presumptively from the previous gastric foreign body surgery. Histopathology determined that a fibrous tissue band caused entrapment of the segment of intestine and its mesentery resulting in volvulus and ischemic necrosis of the intestine. This case is unique because it involved a focal area of the jejunum that was incarcerated in fibrous adhesions.
Disseminated Histoplasmosis Accompanied by Cutaneous Fragility in a Cat
Authors: Tamulevicus Amy M. , Harkin Kenneth , Janardhan Kyathanahalli , Debey Brad M.
Published: April 2011

A 4 yr old, spayed female domestic shorthair was referred with a 2 mo history of weight loss, anorexia, and diarrhea. Skin fragility was noted on presentation and a large skin tear measuring 5 cm × 5 cm was obvious over the dorsal cervical region. The patient was previously treated with short-term prednisone that was discontinued 6 wk before presentation. Initial diagnostics (complete blood count and biochemistry) did not indicate an endocrine disorder, the most common cause of acquired feline skin fragility. Necropsy revealed diffuse histoplasmosis (most significantly affecting the skin), epidermal atrophy, dermal collagen separation, and infiltration in the dermis and subcutis by inflammatory cells containing yeast organisms consistent with Histoplasma spp. Infiltrative fungal infection should be considered as a potential cause of acquired feline skin fragility.
Treatment with DAV for Advanced-Stage Hemangiosarcoma in Dogs
Authors: Dervisis Nikolaos G. , Dominguez Pedro A. , Newman Rebecca G. , Cadile Casey D. , Kitchell Barbara E.
Published: April 2011

Hemangiosarcoma (HSA) is an aggressive disease that is fairly common in the dog. The authors evaluated a doxorubicin, dacarbazine, and vincristine (DAV) combination protocol in dogs with nonresectable stage II and stage III HSA. Twenty-four dogs were enrolled in this prospective, phase 2 study. Doxorubicin and dacarbazine were administered on day 1 while vincristine was administered on days 8 and 15. The protocol was repeated every 21 days for a maximum of six cycles or until disease progression. Toxicity and efficacy were assessed by clinical and laboratory evaluation and by questionnaires completed by the owners. Of the 24 included dogs, 19 were evaluable for response. The response rate (including five complete responses and four partial responses) was 47.4%. Median time to tumor progression was 101 days and median overall survival was 125 days. Significant toxicities were noted, including 41 high-grade hematologic and 12 high-grade gastrointestinal toxic events. Five dogs discontinued treatment due to chemotherapy-related toxicities, but no treatment-related deaths occurred. Multivariate analysis identified patient age (relative risk [RR], 2.3, P=0.049) to be negatively associated with time to progression whereas dacarbazine dose reductions (RR, 0.06, P=0.031) were positively associated with time to progression. Dacarbazine dose reduction was the sole factor positively associated with overall survival (RR, 0.28, P=0.015). In conclusion, the DAV combination appears to offer clinical responses and may prolong survival in dogs with advanced-stage HSA.
Contrast-Enhanced CT for Localizing Compressive Thoracolumbar Intervertebral Disc Extrusion
Authors: Schroeder Regina , Pelsue Davyd H. , Park Richard D. , Gasso Daniel , Bruecker Kenneth A.
Published: April 2011

Thoracolumbar intervertebral disc extrusion is a common disease in dogs. Surgical decompression of the spinal cord is the preferred treatment. Localization of the compressive material is critical for surgical planning. Myelography has been used for localizing extruded disc material, but this procedure carries risk of complications. Computed tomography (CT) is becoming more available for use in veterinary medicine and CT myelography is used for localization of extruded disc material. This report compares CT with intravenous contrast medium and CT myelography for identifying extruded intervertebral discs. CT with intravenous contrast medium is as effective as CT myelography for determining level and laterality of compressive disc extrusions.
Iron Homeostasis and Disorders in Dogs and Cats: A Review
Authors: McCown Jennifer L. , Specht Andrew J.
Published: April 2011

Iron is an essential element for nearly all living organisms and disruption of iron homeostasis can lead to a number of clinical manifestations. Iron is used in the formation of both hemoglobin and myoglobin, as well as numerous enzyme systems of the body. Disorders of iron in the body include iron deficiency anemia, anemia of inflammatory disease, and iron overload. This article reviews normal iron metabolism, disease syndromes of iron imbalance, diagnostic testing, and treatment of either iron deficiency or excess. Recent advances in diagnosing iron deficiency using reticulocyte indices are reviewed.
Dirofilaria immitis Infection in Dogs from Underserved, Native American Reservations in the United States
Authors: Theis Jerold H. , Kass Philip H. , Davis Eric , Stevens Fred , Wojdak Windi
Published: April 2011

Blood samples from 1,822 dogs residing on Native American reservations in 10 states were collected between February 2004 and August 2007. Samples were examined using a commercial enzyme-linked immunosorbent assay (ELISA) antigen capture test. All ELISA-positive samples were subsequently examined for microfilaremia. All dogs were asymptomatic for Dirofilaria immitis infection, resided outside (except for winter in the Northern latitudes), not on prophylaxis for D. immitis, and had not traveled off of the reservation. Reservations were characterized by degrees of north latitude, true prevalence of D. immitis, and a reproductive index calculated by multiplying the number of months of the year in which infective stage larvae (L3) could develop in 30 days or less for each reservation by the 30 yr mean annual rainfall in centimeters recorded for that community. The prevalence of heartworm was directly related to the reproductive index on each reservation.
Experimental Pharmacodynamics and Analgesic Efficacy of Liposome-Encapsulated Hydromorphone in Dogs
Authors: Krugner-Higby Lisa , Smith Lesley , Schmidt Brynn , Wunsch Laura , Smetana Andrea , Brown Carolyn , Heath Timothy D.
Published: April 2011

The purpose of this study was to determine the experimental side effects of liposome-encapsulated hydromorphone (LE-Hydro) in beagles and to evaluate LE-Hydro analgesia in dogs undergoing ovariohysterectomies (OVH). Beagles were injected subcutaneously with 1–3 mg/kg LE-Hydro or 0.1 mg/kg hydromorphone. Dogs were evaluated for sedation, temperature, respiratory rate, and heart rate. OVH dogs were injected with 2 mg/kg LE-Hydro subcutaneously or 0.2 mg/kg morphine and 0.05 mg/kg acepromazine intramuscularly. Side effects of LE-Hydro were within clinically acceptable limits. The analgesic efficacy was superior in dogs administered LE-Hydro at 12 hr postsurgically. LE-Hydro provided adequate, durable analgesia in dogs undergoing OVH.
Left Ventricular Inflow Tract Obstruction Secondary to a Myxoma in a Dog
Authors: Fernandez-del Palacio M. Josefa , Sanchez Joaquin , Talavera Jesus , Martínez Carlos
Published: April 2011

This is the first description of a left ventricular inflow tract obstruction secondary to a myxoma in a dog. A 4 yr old, male fox terrier presented with a 1 mo history of cough and exercise intolerance. Expiratory dyspnea, pulmonary crackles, irregular cardiac rhythm, and a grade 4/6 pansystolic cardiac murmur over the left cardiac apex were the most important features on physical examination. The electrocardiogram revealed atrial fibrillation. Thoracic radiographs showed left-sided cardiac enlargement and mild pulmonary edema, especially in the hilar area. Two-dimensional transthoracic echocardiography showed severe left atrial dilation and a homogenous, echodense mass involving both leaflets of the mitral valve and the posteromedial papillary muscle, inducing mitral stenosis. Spectral Doppler echocardiography was consistent with severe left ventricular inflow tract obstruction secondary to a mass. Therapy for congestive heart failure was prescribed. Follow-up examinations of the dog 1 mo, 2 mo, and 6 mo after diagnosis showed an improvement in clinical signs, but similar echocardiographic features. Eleven months after diagnosis, the dog was euthanized at the owner's request because of recurrent congestive heart failure. The postmortem examination showed the cardiac tumor was consistent with a myxoma.
Cutaneous MCTs: Associations with Spay/Neuter Status, Breed, Body Size, and Phylogenetic Cluster
Authors: White Carrie R. , Hohenhaus Ann E. , Kelsey Jennifer , Procter-Gray Elizabeth
Published: April 2011

Certain breeds are known to be overrepresented among mast cell tumor (MCT) patients, but other risk factors have not been evaluated. This study presents results from a case-control study of 252 dogs with grade 2 or grade 3 cutaneous MCT. Increased risk for MCT development was found in spayed females (adjusted odds ratio [OR], 4.11), boxers (adjusted OR, 6.09), Labrador retrievers (adjusted OR, 3.95), pugs (adjusted OR, 3.17), golden retrievers (adjusted OR, 2.12), the mastiff and terrier phylogenetic cluster (adjusted OR, 3.19), and breeds classified as large (adjusted OR, 2.10) or giant (adjusted OR, 5.44). Additional studies are needed to evaluate the role of these and other potential risk factors in MCT development.
Pericardial Free Patch Grafting as a Rescue Technique in Surgical Management of Right Atrial HSA
Authors: Morges Michelle , Worley Deanna R. , Withrow Stephen J. , Monnet Eric
Published: April 2011

A 7 yr old, neutered female vizsla underwent an exploratory thoracotomy after diagnosis of recurrent hemorrhagic pericardial effusion and a right auricular mass. Staging tests were negative for metastasis. The patient underwent a right, fourth intercostal thoracotomy, subtotal pericardectomy, right auricular mass excision, and pericardial free patch graft. The patient experienced blood loss during surgery, which required a packed red blood cell transfusion. The patient experienced transient arrhythmias postoperatively, but was discharged from the hospital 48 hr later. Histopathologic diagnosis of the mass was hemangiosarcoma. The patient was treated with carboplatin single-agent chemotherapy and palliative radiation therapy. The patient died at home, presumably from metastatic disease 260 days postoperatively. Surgical mass removal or debulking along with pericardial free patch grafting may be considered as palliative treatment options for dogs diagnosed with right auricular masses. In this case report, other techniques failed to repair the defect in the heart and a free patch graft offered a good rescue procedure with a favorable outcome without the need for inflow and outflow occlusion when used in conjunction with adjunctive therapies.
Survey of Heartworm Prevention Practices Among Members of a National Hunting Dog Club
Authors: Rohrbach Barton W. , Odoi Agricola , Patton Sharon
Published: April 2011

Surveillance data indicate that failures have been reported for virtually all heartworm prevention product categories. Resistance of third and fourth stage larvae of Dirofilaria immitis to macrocyclic lactones, lack of compliance, other unknown factors, or a combination of these reasons may be the cause of failure. A survey of members of a national hunting dog club was conducted to identify practices used to prevent canine heartworm infections. Questionnaires were completed by 708 dog owners. Year-round administration of heartworm preventive medication was reported by 208 (88%) respondents residing north of the 37th parallel. Dosing was based on the estimated weight of the dog by 54 (7%) respondents, 389 (55%) did not record the date prophylaxis was administered, and 89 (13%) observed the dogs spit out pills. Heartworm testing at least once per year was done by 556 (79%) respondents and test dates were spread throughout the year. Only 448 (64%) respondents tested newly acquired dogs for heartworm. These findings suggest that veterinarians should place a greater emphasis on the frequency and timing of heartworm diagnostic tests, the importance of weighing dogs, duration of administration, recording the date monthly heartworm prophylaxis is given, and observing dogs to ensure that oral medication is retained.
Optimization of the microstructure of porous composite cathodes in solid oxide fuel cells
Authors: Farhad Siamak , Hamdullahpur Feridun
Published: April 2011

A comprehensive micromodel to predict the electrochemical performance of porous composite LSM‐YSZ cathodes in solid oxide fuel cells (SOFCs) is developed. The random packing sphere model is used to estimate the cathode microstructural properties required for the micromodel. The micromodel developed takes into account the complex interdependency among the mass transport, electron and ion transports, and the electrochemical reaction, and can be used for optimization of the microstructure of porous LSM‐YSZ composite cathodes. It is shown that the electrochemical performance of these cathodes depends on the microstructural variables of the cathode porosity, thickness, particle size ratio, and size and volume fraction of LSM particles. The effect of these microstructural variables on the cathode total resistance, as the objective function to achieve the optimum microstructure for the cathode, is studied through computer simulation. The results indicated that for a LSM‐YSZ cathode operated at the average temperature of 1073.15 K, bulk oxygen partial pressure of 0.21 atm, and total current density of 5000 Am−2, and constrained to the minimum value of 1 μm for the size of LSM particles and 0.25 for the cathode porosity, the optimum microstructure is obtained at the particle size ratio of unity, LSM particle size of 1 μm and volume fraction of 0.413, porosity of 0.25, and thickness of 60 μm. The cathode total resistance corresponding to the cathode optimized is estimated to be 0.291 Ω cm2. © 2011 American Institute of Chemical Engineers AIChE J, 2012
Adaptation of simple molecular networks to time‐dependent stimulus
Authors: Chang Xiao , Liu Dengyu , Liu Zengrong , Chen Luonan , Wang Ruiqi
Published: April 2011

Adaptation is the ability by which signaling systems reset themselves after responding to a stimulus. Incoherent feedforward loops and negative feedback loops are the only two types of three‐node topologies showing adaptation to constant stimuli. In this study, adaptation of these two types of topologies to time‐dependent stimuli are discussed. Through analytical calculation and numerical simulations, it is found that they may show adaptation when the pulse duration and internal are properly assigned. In particular, for incoherent feedforward loops, two kind of models, i.e., logic approximation piecewise‐linear equations and Hill‐type equations are considered. When adaptation to time‐dependent stimulus is considered, analytical solutions for logic approximation piecewise‐linear equations and numerical simulation for Hill‐type equations are in substantial agreement. The study on adaptation to time‐dependent stimulus could serve as a manual providing different possible solutions to develop intelligent therapeutic strategies and to build biological circuits with specified functions.

Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Carbohydrate–Protein Interactions: A 3D View by NMR
Authors: Roldós Virginia , Cañada F. Javier , Jiménez‐Barbero Jesús
Published: April 2011

This review focuses on the application of NMR methods for understanding, at the molecular and atomic levels, the diverse mechanisms by which sugar molecules are recognised by the binding sites of lectins, antibodies and enzymes. Given the intrinsic chemical natures of sugars and their flexibility, it is well established that NMR parameters should be complemented by computational methods in attempts to unravel the structural and conformational features of the molecular recognition process unambiguously. We therefore aim here to describe new and significant advances in the knowledge of carbohydrate–protein interactions, obtained by employing state‐of‐the‐art NMR and molecular modelling. We have not attempted to prepare an exhaustive review but have tried to focus on describing the key aspects that should be considered when tackling a problem within this research topic.
Stereochemistry and Mechanism of the Brønsted Acid Catalyzed Intramolecular Hydrofunctionalization of an Unactivated Cyclic Alkene
Authors: McKinney Brooner Rachel E. , Widenhoefer Ross A.
Published: April 2011

Through employment of deuterium‐labeled substrates, the triflic acid catalyzed intramolecular exo addition of the XH(D) (X=N, O) bond of a sulfonamide, alcohol, or carboxylic acid across the CC bond of a pendant cyclohexene moiety was found to occur, in each case, with exclusive formation (≥90 %) of the anti‐addition product without loss or scrambling of deuterium as determined by 1H and 2H NMR spectroscopy and mass spectrometry analysis. Kinetic analysis of the triflic‐acid‐catalyzed intramolecular hydroamination of N‐(2‐cyclohex‐2′‐enyl‐2,2‐diphenylethyl)‐p‐toluenesulfonamide (1 a) established the second‐order rate law: rate=k2[HOTf][1a] and the activation parameters ΔH≠=(9.7±0.5) kcal mol−1 and ΔS≠=(−35±5) cal K−1 mol−1. An inverse α‐secondary kinetic isotope effect of kD/kH=(1.15±0.03) was observed upon deuteration of the C2′ position of 1 a, consistent with partial CN bond formation in the highest energy transition state of catalytic hydroamination. The results of these studies were consistent with a mechanism for the intramolecular hydroamination of 1 a involving concerted, intermolecular proton transfer from an N‐protonated sulfonamide to the alkenyl C3′ position of 1 a coupled with intramolecular anti addition of the pendant sulfonamide nitrogen atom to the alkenyl C2′ position.
Photocatalytic Hydrogen Generation from Water with Iron Carbonyl Phosphine Complexes: Improved Water Reduction Catalysts and Mechanistic Insights
Authors: Gärtner Felix , Boddien Albert , Barsch Enrico , Fumino Koichi , Losse Sebastian , Junge Henrik , Hollmann Dirk , Brückner Angelika , Ludwig Ralf , Beller Matthias
Published: April 2011

An extended study of a novel visible‐light‐driven water reduction system containing an iridium photosensitizer, an in situ iron(0) phosphine water reduction catalyst (WRC), and triethylamine as sacrificial reductant is described. The influences of solvent composition, ligand, ligand‐to‐metal ratio, and pH were studied. The use of monodentate phosphine ligands led to improved activity of the WRC. By applying a WRC generated in situ from Fe3(CO)12 and tris[3,5‐bis(trifluoromethyl)phenyl]phosphine (P[C6H3(CF3)2]3, Fe3(CO)12/PR3=1:1.5), a catalyst turnover number of more than 1500 was obtained, which constitutes the highest activity reported for any Fe WRC. The maximum incident photon to hydrogen efficiency obtained was 13.4 % (440 nm). It is demonstrated that the evolved H2 flow (0.23 mmol H2 h−1 mg−1 Fe3(CO)12) is sufficient to be used in polymer electrolyte membrane fuel cells, which generate electricity directly from water with visible light. Mechanistic studies by NMR spectroscopy, in situ IR spectroscopy, and DFT calculations allow for an improved understanding of the mechanism. With respect to the Fe WRC, the complex [HNEt3]+[HFe3(CO)11]− was identified as the key intermediate during the catalytic cycle, which led to light‐driven hydrogen generation from water.
Synthesis and Characterization of a Symmetric Bis(7‐hydroxyflavylium) Containing a Methyl Viologen Bridge
Authors: Diniz Ana M. , Pinheiro Carlos , Petrov Vesselin , Parola A. Jorge , Pina Fernando
Published: April 2011

A symmetric bis(flavylium) constituted by two 7‐hydroxyflavylium moieties linked by a methylviologen bridge was synthesized. The thermodynamic and kinetics of the network of chemical reactions involving bis(flavylium) and the model compound 7‐hydroxy‐4′‐methylflavylium was completely characterized by means of direct and reverse pH jumps (stopped flow) and flash photolysis. Both compounds follow the usual pH‐dependent network of chemical reactions of flavylium derivatives. The equilibrium species of the model compound are the flavylium cation (acidic species) and the trans‐chalcone (basic species) with an apparent pK′a=2.85. In the case of the bis(flavylium) it was possible to characterize by 1H NMR spectroscopy three species with different degrees of isomerization: all flavylium, flavylium‐trans‐chalcone, and all trans‐chalcone. Representation of the time‐dependent mole fraction distribution of these three forms after a pH jump from equilibrated solutions of all‐flavylium cation (lower pH values) to higher pH values, shows that formation of trans‐chalcone is not completely stochastic (two independent isomerizations), the isomerization of one flavylium showing a small influence on the isomerization of the other. The radical of the methyl viologen bridge is formed upon reduction of the bis(trans‐chalcone) with dithionite. The system is reversible after addition of an oxidant in spite of the occurrence of some decomposition.
Absolute configurations and stability of cyclic guanosine mono‐adducts with glyoxal and methylglyoxal
Authors: Lai Congfang , Lin Guangxin , Wang Wenyue , Luo Hai
Published: April 2011

Glyoxal and methylglyoxal are two endogenous and mutagenic 1,2‐dicarbonyl compounds, which can readily form adducts with guanosine. The molecular structures of cyclic guanosine‐glyoxal (G‐g) and guanosine‐methylglyoxal (G‐mg) mono‐adducts have been extensively studied before. However, diastereoisomers of these adducts have not yet been studied in detail. In this work, one pair of G‐g and two pairs of G‐mg diastereoisomers were baseline separated by reverse phase HPLC, whose structures were identified as the previously reported cyclic forms, and their absolute configurations were determined by circular dichroism, the octant rule, and molecular modeling. According to the HPLC elution order, configurations of two G‐g (as well as trans G‐mg) were (6R,7R) and (6S,7S), respectively. Meanwhile, the stability of each isomer in neutral solution was also investigated, which revealed the stability order G‐g > cis G‐mg > trans G‐mg and also indicated distinct transformation processes for different G‐mg configurations. Trans G‐mg only racemized between each other, while cis G‐mg transformed to both cis and trans forms. Different intermediates in the racemization processes were proposed to explain the observations. These results may shed light on further understanding the roles of these two small molecules in mutagenesis. Chirality, 2011. © 2011 Wiley‐Liss, Inc.
Enantiomeric separation of triazole fungicides with 3‐μm and 5‐μml particle chiral columns by reverse‐phase high‐performance liquid chromatography
Authors: Qiu Jing , Dai Shouhui , Zheng Chuangmu , Yang Shuming , Chai Tingting , Bie Mei
Published: April 2011

This study used chiral columns packed with 3‐μm and 5‐μm particles to comparatively separate enantiomers of 9 triazole fungicides, and Lux Cellulose‐1 columns with chiral stationary phase of cellulose‐tris‐(3,5‐dimethylphenylcarbamate) were used on reverse‐phase high‐performance liquid chromatography with flow rates of 0.3 and 1.0 mL min−1 for 3‐μm and 5‐μm columns, respectively. The (+)‐enantiomers of hexaconazole (1), tetraconazole (4), myclobutanil (7), fenbuconazole (8) and the (−)‐enantiomers of flutriafol (2) diniconazole (3), epoxiconazole (5), penconazole (6), triadimefon (9) were firstly eluted from both columns, the elution orders identified with an optical rotation detector didn't change with variety of column particles and mobile phases (acetronitrile/water and methanol/water). The plots of natural logarithms of the selectivity factors (ln α) for all fungicides except penconazole (6) versus the inverse of temperature (1/T) were linear in range of 5–40°C. The thermodynamic parameters (ΔH°, ΔS°, ΔΔH° and ΔΔS°) were calculated using Van't Hoff equations to understand the thermosynamic driving forces for enantioseparation. This work will be very helpful to obtain good enantiomeric separation and establish more efficient analytical method for triazole fungicides. Chirality, 2011. © 2011 Wiley‐Liss, Inc.
Chiral gas chromatography as a tool for investigations into illicitly manufactured methylamphetamine
Authors: Morrison Calum , J Smith Frank , Tomaszewski Tomasz , Stawiarska Karolina , Biziuk Marek
Published: April 2011

The aim of this study was to develop a chiral gas chromatographic method for the separation of compounds likely to be found in the EMDE synthesis of methylamphetamine, a heavily abused stimulant drug. Here we describe the separation of the enantiomers of ephedrine, pseudoephedrine, chlorinated intermediates and methylamphetamine using fluorinated acid anhydrides as chemical derivatization reagents prior to gas chromatographic analysis on a 2,3‐di‐O‐methyl‐6‐t‐butyl silyl‐β‐cyclodextrin stationary phase (CHIRALDEX™ B‐DM). Separation of the enantiomers of pseudoephedrine, methylamphetamine and chloro‐intermediates was achieved using PFPA derivatization, and enantiomers of ephedrine using TFAA derivatization, in run times of less than 40 minutes. The use of HFBA as a derivatization reagent for this set of analytes is also discussed. Chirality, 2011. © 2011 Wiley‐Liss, Inc.
Application of Magnetic Filters in Bioprocess Engineering. Part 3 – New Measuring Method for Quantification of Magnetic Beads in Flowing Suspensions
Authors: Kampeis Percy , Lieblang Michael , Krause Hans‐Joachim
Published: April 2011

Die Hochgradienten‐Magnetseparation (HGMS) erlaubt eine Fest/Fest/Flüssig‐Trennung in einem Schritt und eignet sich daher als erster Capture‐Schritt in Aufbereitungsverfahren für biotechnologische Produkte. Während der Magnetfiltration bilden sich Magnetbead‐Anlagerungsbereiche aus. Es besteht die Möglichkeit, dass die durchströmende Biomasse einen Teil der Magnetbeads und damit auch sorbiertes Produkt mitreißt. Für den sicheren Prozessbetrieb des HGMS‐Filters muss die Magnetbead‐Konzentration in der den Filter verlassenden Suspension auch in Gegenwart von Biomasse bestimmt werden. Hierzu wurde ein Messverfahren mit einem Durchfluss‐Magnetsensor zur Quantifizierung der Magnetbeads in strömenden Suspensionen entwickelt.
Ring‐size effect in the reaction of α,ω‐dibromoalkanes with ethyl acetoacetate and its application to the synthesis of some disubstituted oxa‐ and aza‐heterocycles
Authors: Yong‐Yue Lin , Xiao‐Guang (Hiu‐Kuang Leung) Liang , Yuk‐Yee Chan
Published: April 2011

Under basic condition, β‐ketoester has two sites at which alkylation can occur. In the reaction of ethyl acetoacetate with α, ω‐dibromoalkanes (n = 2, 3, 4), the alkylation is dependent on the ring size of the possible cyclic product formed. When n = 2 or 4, cyclopropane 3 or cyclopentane 10 was formed, respectively, as a result of two successive C‐alkylations. However, when n = 3, dihydropyran 7 was formed, arising from a C‐alkylation followed by an alkylation. For the last case, the formation of the six‐member ring is the driving force of the whole process. Cyclopropane 3, when treated with an aromatic amine, was transformed to dihydropyrrole 15 via the possible intermediate of cyclopropyl Shiff's base 14. However, similar reaction was not observed for cyclopentane 10. We attribute this phenomenon to the ring‐size effect again, as in the former case, the steric strain of the cyclopropane ring is released during the rearrangement of the Schiff's base to the final product.
Investigation on preparation and structure of YSr2‐x Cax V3O9‐y
Authors: Jian Meng , Yu‐Fang Ren , Ping He
Published: April 2011

New rare earth vanadates YSr2‐xCaxCaxV3O9‐y (x—0.0, 0.67, 1.0, 1.33 and 2.0) have been synthesized by a new simple method. X‐ray powder diffraction results show that they are mono‐phase. They belong to orthorhombic structure and their lattice constants are calculated. The results of weight gains in TG curves show that the lower valent vanadium is oxidized to higher valent state at higher temperature. The oxygen contents of new compounds are calculated from the weight gains. Both V3+ and V4+ coexist in YSr2‐xCaxV3O9‐y. These compounds exhibit low electric resistivity at room temperature.
Studies on sulfinatodehalogenation: XVII. The sulfinatodehalogenation of primary perfluoroalkyl iodides and bromides by Rongalite
Authors: Bing‐Nan Huang , Jin‐Tao Liu
Published: April 2011

Using acetonitrile or DMF as cosolvent, both perfluoroalkyl iodides such as Cl(CF2)nI (n = 4,6,8, la—lc), CF3 (CF2)n I (n = 5,6,7, ld—lf), I (CF2)n O (CF2) SO3 Na(n = 2,4,6, lg—li) and perfluoroalkyl bromides such as Cl (CF2)n Br (n = 4,6, 3a—3b) and C7F15 Br (3e) reacted with Rongalite in aqueous solution to give the corresponding sulfinates Cl (CF2)n SO2 Na (n = 4,6,8, 2a—2c), CF3‐(CF2)nSO2Na (n = 5,6,7, 2d—2f) and NaO2S(CF2)nO(CF2)2SO3Na (n = 2,4,6, 2g—2i) in moderate yields. 1 H‐perfluoroalkanes were formed as the main products when other solvents such as ethanol. iso‐propanol, 1,4‐dioxane and morpholine were used.
The reaction of perfluoroalkanesulfinates: IV. Perfluoroalkyl radical addition to olefins initiated by single electron oxidation of perfluoroalkanesulfinate
Authors: Wei‐Yuan Huang , Yuan Xie
Published: April 2011

Sodium perfluoroalkanesulfinates [Cl (CF2)n SO2 Na (1), a, n = 4; b, n = 6; c, n = 8] with the reduction potentials about 0.95—1.00V could be oxidized readily with various oxidizing agents such as Mn (OAc)3 2H2O, Ce (SO4)2, HgSO4 and Co2O3 to generate perfluoroalkyl radicals which added to the olefins RCH  CHR' to give two kinds of adducts, namely RCH (Rf) CHXR' (3, X  H; 4, X  OAc), with good yields depending upon the solvent system used. Different oxidizing agents showed slight variation on the yields of the adducts. The reaction time could be greatly shortened at higher temperature. Thus, this reaction provides a new way for introducing a perfluoroalkyl group into olefinic compounds.
A study on the sulfenylchlorination of cembrene and the related cembranoids
Authors: Zhu‐Jin Liu , Yun‐Long Li , Qing‐Zhi Chen , Wei‐Qi Wang
Published: April 2011

p‐Tolylsulfenyl chloride adds regioselectively at the C(11)  C(12) bond of cembrene 1 to give 11‐(R)‐p‐tolylthio‐1‐(S)‐cembra‐2E, 4Z, 7E, 12(20)‐tetraene 2 following a rapid HCl elimination. Two new cembranoids, 1‐(S)‐cembra‐2E, 4Z, 7E, 12(20)‐tetraene 3 and 1‐(S)‐cembra‐2E, 4Z, 7E, 11Z‐tetraen‐20‐ol 4 are prepared from 2.
AC impedance study on semiconducting properties of anodic plumbous oxide film
Authors: Cong Pu , Zhuo‐Li He , Hou‐Tian Liu , Xia‐Lin Chen , Wei‐Fang Zhou
Published: April 2011

The semiconducting properties of anodic film formed on Pb in 4.5mol·dm−3H2SO4 solution (30°C) at 0.9 V (vs. Hg/Hg2SO4) for 2 h were studied using AC impedance method. The phase composition of the film is PbSO4 and PbO·PbSO4. The semiconducting properties are due to the latter. The Mott‐Schottky plots show that the said film is an n‐type semiconductor with flat‐band potential of −0.9 V (vs. Hg/Hg2SO4) and donor density of 1×1016 cm−3. The surface density measured at 410–2500 Hz is (2–5)×1012 cm−2 eV−1.
A DNMR study on the ring inversion of oxazolidines
Authors: Li Yang , Kun Gao , Su‐Ling Kong , Yao‐Zu Chen
Published: April 2011

Ring inversion of eight substituted 2‐phenyl‐4, 4‐dimethyloxazolidines in o‐dichlorobenzene‐d4 was studied by 1H DNMR. Very high inversion barriers (ΔGo≠ = 86.7–93.4 kJ·mol−1) were found for these oxazolidine rings. The magnitude of the inversion barrier is dependent on the polarity of the substituent on the phenyl group. A linear correlation is present between the ΔGo≠ of the inversion and the substituent constant, σ+, of the substituent.
A novel 2‐C reactivity studies of 1‐aroyl‐1,2‐dihydro‐3H‐naphtho[2,1‐b]pyran‐3‐ones
Authors: El‐Kasaby  , Hassan  , Shiba  , Abou‐El‐Regal
Published: April 2011

The 2‐C, methylene group of 1‐aroyl‐1,2‐dihydro‐3H‐naphtho[2,1‐b]pyran‐3‐ones (2) have been showed to possess a superior reactivity towards many of organic reagents. The naphthopyrones (2) condensed with aromatic aldehydes to give the 2‐arylidine derivatives (3). Bromination of 2 gave 1,2‐dibromo (4) or 5‐bromo (5) derivatives depending on the reaction conditions. The base catalyzed addition or cycloaddition of naphthopyrones (2) to 4‐methoxy benzalacetophenone gave the expected Michael adduct (6) or the cyclic adducts (7–9) depending on the type of catalytic base and reaction conditions. Structures of the products have been established by elemental analyses, IR and 1H NMR spectroscopic methods.
Studies on the alcohol exchange reactions of methoxide ditungsten [W(IV)] compound W2Cl4(OCH3)4 (CH3OH)2, prepared from (n‐Bu4N)3W2Cl9
Authors: Hong Bo , Jin Song‐Lin , Yih‐Tong (Gu, Yi‐Dong) Ku , Chen Ming‐Qin
Published: April 2011

(n‐Bu4N)3W2Cl9, prepared from K3W2Cl9, can be readily converted to a series of [W(IV)] cluster compounds, W2Cl4 (μ‐OR)2 (OR')2 (R'OH)2, including seven known compounds and two new compounds with R=Me, R'=i‐Pr and sec‐Bu. The crystallographic data of 7 and 8 are hereby presented.
Influence of Negative Ions on Drift Waves in a Low‐Density Ar/O2‐Plasma
Authors: Knist S. , Greiner F. , Biss F. , Piel A.
Published: April 2011

The effect of negative ions on the drift wave instability has been studied in detail in a linear device by means of Langmuir probes and cross‐correlation analysis. Drift waves are excited in low‐density (5 × 1014 m–3) and strongly magnetized (0.5 T) pure argon plasmas and in the presence of an oxygen admixture. The radial density profile of negative ions is hollow. For increasing concentration of negative ions the wave frequency decreases by about 25%. Despite of an axial density gradient, a global wave frequency is established for the entire column length. While for the noble gas case the drift wave frequency is given by the equilibrium plasma parameters in the mid‐plane, there is no such relationship for the argon plasma with oxygen admixture. This different finding is attributed to the inhomogeneous distribution of the negative ions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dust Self‐Organized Structures II. Solutions of Master Equations for Small Diffusion
Authors: Tsytovich V. , Morfill G.
Published: April 2011

Master equations for spherical dust structures are solved numerically using the asymptotic solutions at the center of the structures for the case of absence of external ionization and small diffusions. The structures are determined by a single parameter, the external plasma flux at the surface of the structure. The equilibrium states that are possible in a limited range of this parameter are investigated numerically. It is demonstrated that in the range of existence of equilibria the structures are changing their shapes and type of distributions inside the structures. For large external fluxes the ion and dust distributions can have peaks inside the structures while for low external fluxes the dust distribution has a single maximum at the structure center. The lower is the external flux supporting the structure the larger is its size. An increase of the external flux decreases the accumulation of dust and ions at the center. The total number of dust confined by the structure is larger for larger size structures. Estimates of dust crystallization inside structures are given. The role of diffusion is calculated by perturbations and is shown to be small in all structure regions except the structure edges. In the perturbation theory we use the exact expressions of the diffusion coefficients calculated previously numerically. The regions with dust density peaks inside the structures have been calculated with two order of magnitude larger precision that allows to resolve the structure parameter dependencies inside the peaks. It is shown that although in peaks the gradients of all parameters are increased the diffusion flux is still small and that the continuity and hydrodynamic approach are applicable within an accuracy about several %‐s (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dust Self‐Organized Structures III. Solutions of Master Equations in Presence of Volume Ionization
Authors: Tsytovich V. , Morfill G.
Published: April 2011

The shapes of dust self‐organized structures in presence of volume ionization is investigated. Master Equations for small diffusions and presence of an external ionization describing spherical dust structures are solved numerically using asymptotic solutions at the center of the structures. The structures are determined by two parameters, the external plasma flux at the surface of the structures and the power of volume ionizations. It is shown that the range of possible equilibrium states is reduced with an increase of the ionization power. This reduction is due mainly to an increase of the minimum possible value of ion density at the center of the structure for which the equilibrium is possible (an increase of minimum possible external flux). It is found that for certain large ionization power the equilibrium structure without void at the center cannot exist. The critical value of ionization power is found numerically. In the range of ionization power where the equilibria is possible the distribution of the parameters inside the structures are investigated by solving the Master Equations in the limits of small and large ionization power (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)