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Steven D Brown

Publications and source records attributed to Steven D Brown.

At least 19 recordsLinked to original sources
PubMed2004

Wavelet multiscale regression from the perspective of data fusion: new conceptual approaches.

Wavelet regression is a very promising technique for modern multivariate calibration and calibration transfer. Multiscale analysis of wavelet scales provides a connection between wavelet regression and data fusion. In this paper, current wavelet regression methods are reviewed from the novel perspective of data fusion. Illustrated by analysis of a public domain near-infrared dataset, the advantages and drawbacks of these methods are examined. For wavelet regression, the non-uniformity of the wavelet components, the multiscale nature of the signal, and the prevention of information leakage are crucial issues that will be addressed.

Journal Article↗
PubMed2004

Transfer of multivariate calibrations between four near-infrared spectrometers using orthogonal signal correction.

The transfer of partial least squares (PLS) calibration models among four near-infrared spectrometers was investigated for the quantitative analysis of thermoset resin polymers. A comparative study of second derivatives, multiplicative scatter correction, finite impulse response filtering, slope and bias correction, model updating (MU), and orthogonal signal correction (OSC) was conducted to determine which processing methods achieved model transferability. It is shown that OSC and MU were superior to the other calibration transfer methods, leading to very robust PLS models with enhanced predictive ability. It is also shown that the transfer results obtained with OSC were not significantly different from those obtained with model updating.

Journal Article↗
PubMed2004

Hydrogenolysis of [PhBP3]Fe[triple bond]N-p-tolyl: probing the reactivity of an iron imide with H2.

This paper describes the reductive hydrogenolysis of a low-spin (S = 1/2) iron(III) imide. Pseudotetrahedral [PhBP3]FeIIIN-p-tolyl is reduced by hydrogen at ambient temperature and pressure in benzene solution. The reduction appears to proceed in a stepwise fashion. An intermediate S = 2 iron(II) anilide, [PhBP3]Fe(N(H)-p-tolyl), is observed and has been independently generated and structurally characterized. Prolonged hydrogenolysis in benzene results in the complete hydrogenolysis of the Fe-N linkage to release H2N-p-tolyl. The major iron-containing product formed from this step is the diamagnetic cyclohexadienyl complex, [PhBP3]Fe(eta5-cyclohexadienyl), which has also been independently prepared and structurally characterized. Evidence is presented to suggest that the final [PhBP3]Fe(eta5-cyclohexadienyl) product is formed via benzene insertion into a reactive [PhBP3]FeII-H intermediate.

Journal Article↗
PubMed2004

Comparative in vitro activity of telithromycin and beta-lactam antimicrobials against community-acquired bacterial respiratory tract pathogens in the United States: findings from the PROTEKT US study, 2000-2001.

BACKGROUND: Telithromycin is a new ketolide antimicrobial that was developed to provide good activity against resistant respiratory tract pathogens. PROTEKT US (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin in the United States) is a multicenter in vitro surveillance study that was initiated in 2000 to chart the emergence and spread of antimicrobial-resistant pathogens in patients with community-acquired respiratory tract infections (CARTIs). OBJECTIVE: This article reports first-year results from PROTEKT US pertaining to the comparative in vitro activity of telithromycin and beta-lactam antimicrobials against community-acquired bacterial respiratory tract pathogens. METHODS: Data were compiled on the comparative in vitro activity of telithromycin and beta-lactams against Streptococcus pneumoniae (10,103 isolates), Streptococcus pyogenes (3918 isolates), and Haemophilus influenzae (2706 isolates). Minimum inhibitory concentrations (MICs) and susceptibilities were determined according to National Committee for Clinical Laboratory Standards methods. RESULTS: In total, 38.8% (3920/10,103) of pneumococcal isolates were not susceptible to penicillin (12.5% [1266] intermediate [MIC, > or =0.12-1.0 mg/dL], 26.3% [2654] resistant [MIC, > or =2 mg/dL]). Telithromycin was highly active against S pneumoniae (MIC required to inhibit 90% of isolates [MIC(90)], 0.5 mg/L), with 99.6% (10,062/10,103) of isolates fully susceptible (MIC, < or =1 mg/L). Based on MIC(90)s, the rank order of antimicrobial activity was telithromycin (0.5 mg/L), followed by amoxicillin/clavulanate (2 mg/L), penicillin (4 mg/L), and cefuroxime (8 mg/L). Telithromycin retained high activity (MIC(90), 1 mg/L) against penicillin-resistant penumococci that showed high levels of coresistance to beta-lactams. All isolates of S pyogenes were fully susceptible to the beta-lactams tested. Beta-lactamase production was common among H influenzae isolates (28.3% [765/2706]). Telithromycin was active against H influenzae (MIC(90), 4 mg/L), irrespective of beta-lactamase production. CONCLUSION: Overall, these findings from the first year of PROTEKT US support the potential value of telithromycin in the treatment of CARTIs.

Anti-Bacterial Agents↗
PubMed2004

Antibacterial susceptibility among Streptococcus pneumoniae isolated from paediatric and adult patients as part of the PROTEKT US study in 2001-2002.

BACKGROUND: One of the main factors commonly associated with antibacterial resistance among Streptococcus pneumoniae is the age of the patient. The highest rates of resistance have often been reported among isolates from young children. METHODS: Data from the PROTEKT US (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin in the United States) surveillance study were examined to determine the level of antibacterial resistance among S. pneumoniae isolates collected in 2001-2002 from different patient age groups in the USA. RESULTS: A total of 10 012 clinical isolates of S. pneumoniae were submitted by 242 centres across the USA and categorized into four patient age groups: infants (0-2 years, n = 1556), children (3-14 years, n=1125), adults (15-64 years, n=4058) and elderly adults (> or =65 years, n = 3067) (age unknown n=206). With the exception of the fluoroquinolones and linezolid, rates of antibacterial resistance were highest among infants and decreased with increasing patient age. Resistance to penicillin ranged from 33.6% among infants to 17.5% among elderly adults, and erythromycin resistance ranged from 41.1% among infants to 24.0% among adults. In contrast, levofloxacin resistance increased with patient age (from 0.1% to 1.6%). The highest rates of susceptibility were noted for telithromycin and linezolid (> or =99.6% and > or =99.8% susceptible isolates, respectively). CONCLUSIONS: The PROTEKT US study data confirmed that the highest antibacterial resistance rates were associated with isolates collected from young children (0-2 years). Telithromycin may offer a reliable alternative to first-line drugs in the empirical treatment of community-acquired respiratory tract infections.

Adolescent↗
PubMed2004

Antimicrobial susceptibility of Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae collected from patients across the USA, in 2001-2002, as part of the PROTEKT US study.

BACKGROUND: The PROTEKT US (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin in the United States) surveillance programme was started in 2000, to chart the emergence and spread of antimicrobial resistance among isolates of Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae from across the USA. METHODS: In 2001-2002 (Year 2 of PROTEKT US) 242 centres from 46 states and the territory of Puerto Rico submitted a total of 10 012 S. pneumoniae, 4508 S. pyogenes and 3296 H. influenzae isolates from community-acquired respiratory tract infections (CARTIs). Susceptibility testing was performed and interpreted using NCCLS methodology and criteria. RESULTS: Overall, 35.4% of S. pneumoniae were non-susceptible to penicillin (14.2% intermediate, MIC 0.12-1 mg/L; 21.2% resistant, MIC > or =2 mg/L) and 27.9% were resistant to erythromycin (MIC > or =1 mg/L) (0.2% intermediate, MIC 0.5 mg/L). A total of 105 (1.0%) isolates were resistant to levofloxacin (MIC > or =8 mg/L). More than 99.2% of isolates were susceptible to telithromycin (MIC < or =1 mg/L) irrespective of penicillin and/or erythromycin resistance. All S. pyogenes isolates were susceptible to penicillin (MIC < or =0.12 mg/L) and 5.7% were resistant to erythromycin (MIC > or =1 mg/L) (0.3% intermediate, MIC 0.5 mg/L). The MIC90 of telithromycin for S. pyogenes was 0.03 mg/L. A total of 27.5% of H. influenzae isolates were beta-lactamase producers. Overall, 27.8% were resistant (MIC > or =4 mg/L) and 1.1% were intermediate to ampicillin (MIC 2 mg/L). A total of 96.3% of H. influenzae isolates were susceptible to telithromycin (MIC < or =4 mg/L). CONCLUSIONS: Antimicrobial resistance continues to be a problem in the USA. The ketolide telithromycin continues to show high activity against common CARTI pathogens, including those resistant to beta-lactams and macrolides.

Anti-Infective Agents↗
PubMed2004

Prevalence and molecular analysis of macrolide and fluoroquinolone resistance among isolates of Streptococcus pneumoniae collected during the 2000-2001 PROTEKT US Study.

The PROTEKT US (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin in the United States) surveillance program was established to determine the prevalence and mechanisms of antibacterial resistance among bacterial pathogens from patients with community-acquired respiratory tract infections. In year 1 of the PROTEKT US study, 10,103 isolates of Streptococcus pneumoniae, including 3,133 erythromycin-resistant strains and 81 levofloxacin-resistant strains, were collected from 206 centers. We report on the molecular analyses of these resistant strains. The resistance genotypes among the 3,044 typed macrolide-resistant isolates overall were mef(A) (n = 2,157; 70.9%), erm(B) (n = 530; 17.4%), mef(A) erm(B) (n = 304; 10.0%), and erm(A) subclass erm(TR) (n = 5; 0.2%). Fifty (1.6%) macrolide-resistant isolates were negative for the mef and the erm resistance genes. Seventy-eight (96.3%) of the 81 levofloxacin-resistant isolates analyzed possessed multiple mutations in the gyrA, gyrB, parC, and/or parE quinolone resistance-determining regions. A total of 43 known multilocus sequence typing (MLST) profiles (or single- or double-locus variants) accounted for 75 of 81 isolates. There was no evidence of dissemination of fluoroquinolone-resistant clones within the United States; however, 12 isolates with the same MLST profile were located in one center in Massachusetts. Almost 90% of the erythromycin-resistant isolates and approximately one-third of the levofloxacin-resistant isolates were multidrug resistant.

Anti-Bacterial Agents↗
PubMed2004

Broth microdilution susceptibility testing of Francisella tularensis: quality control limits for nine antimicrobial agents and three standard quality control strains.

For broth microdilution susceptibility tests of Francisella tularensis, Mueller-Hinton broth with 2% Isovitalex is recommended. Using that medium, we studied three standard control strains tested with nine antimicrobial agents potentially efficacious for treating tularemia. An eight-laboratory collaborative study generated the data needed to propose appropriate MIC control limits.

Anti-Bacterial Agents↗
PubMed2003

A low-spin d5 iron imide: nitrene capture by low-coordinate iron(I) provides the 4-coordinate Fe(III) complex [PhB(CH2PPh2)3]Fe=N-p-tolyl.

Entry into "[PhBP3]Fe" chemistry affords a rare, pseudotetrahedral iron(I) complex, [PhBP3]Fe(PPh3), with an S = 3/2 ground state. This precursor undergoes rapid oxidation by aryl azide to produce the d5 imide [PhBP3]FeNAr (Ar = p-tolyl). The Fe(III) imide is significant in that it is low-spin and represents the first mononuclear imide of iron. Doublet [PhBP3]FeNAr reacts rapidly and quantitatively with CO at room temperature to release isocyanate and [PhBP3]Fe(CO)2. The [PhBP3]Fe(CO)2 byproduct is also a precursor to [PhBP3]FeNAr upon addition of aryl azide.

Biomimetic Materials↗
PubMed2003

Acute pancreatitis in intensive care unit patients: value of clinical and radiologic prognosticators at predicting clinical course and outcome.

OBJECTIVE: To assess the value of clinical and/or radiographic prognostic indices in predicting the clinical course and outcome of patients with acute pancreatitis, in the intensive care unit. DESIGN: Retrospective, single institution review. SETTING: An adult medical and surgical intensive care unit in a public, urban teaching hospital. PATIENTS: Patients with acute pancreatitis requiring intensive care unit admission between January 1, 1997 and June 30, 2000. INTERVENTIONS: Standard care. MEASUREMENTS AND MAIN RESULTS: A total of 477 patients were hospitalized with the diagnosis of acute pancreatitis. Of these, 28 patients (6%) were admitted to the intensive care unit. Ranson's, Imrie scores, Acute Physiologic and Chronic Health Evaluation (APACHE) II and III scores, simplified acute physiology scores, and multiple organ dysfunction scores were tabulated at 1, 2, 3, 7, and 14 days after intensive care unit admission. Abdominal computed tomography was available for review for 24 of the 28 patients (86%), where the mean Balthazar's computed tomography index was 4.5 +/- 0.4 (range = 2 to 10). Hospital mortality rate for the intensive care unit patients was 14% (4 of 28). The intensive care unit length of stay ranged from 1 to 79 days (mean 15 days, median 5 days). Fifty-seven percent of the patients developed organ dysfunction, and 36% of the patients required mechanical ventilatory support, ranging in duration from 1 to 70 days. Infectious morbidity occurred in 43% of patients. Thirty-six percent of the patients required operative intervention for intraabdominal complications. APACHE II scores at 7 days after intensive care unit admission correlated closely with ventilator days (r2 =.90; p =.003) and correlated with the occurrence of infectious complications (r2 =.71; p =.02). Patient age, APACHE III, simplified acute physiology scores, multiple organ dysfunction scores, Ranson, Imrie, computed tomography, and APACHE II scores before day 7 did not closely correlate with the occurrence of adverse clinical outcome. CONCLUSIONS: The clinical course and outcomes of intensive care unit patients with acute pancreatitis can be highly variable. An APACHE II score <10 during the initial 48 hrs correlated with mild pancreatitis and uncomplicated intensive care unit course; however, multifactorial prognosticators were not useful for the early identification of patients who developed complications or required extended intensive care unit care.

APACHE↗
PubMed2003

Improved piecewise orthogonal signal correction algorithm.

Piecewise orthogonal signal correction (POSC), an algorithm that performs local orthogonal filtering, was recently developed to process spectral signals. POSC was shown to improve partial leastsquares regression models over models built with conventional OSC. However, rank deficiencies within the POSC algorithm lead to artifacts in the filtered spectra when removing two or more POSC components. Thus, an updated OSC algorithm for use with the piecewise procedure is reported. It will be demonstrated how the mathematics of this updated OSC algorithm were derived from the previous version and why some OSC versions may not be as appropriate to use with the piecewise modeling procedure as the algorithm reported here.

Algorithms↗
PubMed2002

In vitro activity of telithromycin against Streptococcus pneumoniae resistant to other antibiotics, including cefotaxime.

A total of 407 isolates of Streptococcus pneumoniae, most of which were resistant to one or more antibiotics, were tested for susceptibility to telithromycin and four other agents. Telithromycin was the most active agent tested, with 98% of isolates susceptible to < or = 1.0 mg/L. For strains resistant to the other antibiotics, susceptibility to telithromycin ranged from 98.6% for strains resistant to trimethoprim/sulfamethoxazole to 94.4% for strains resistant to cefotaxime.

Anti-Bacterial Agents↗
PubMed2002

In vitro bactericidal activity of daptomycin against staphylococci.

MICs and minimum bactericidal concentrations (MBCs) of daptomycin, vancomycin, linezolid and quinupristin-dalfopristin (Q-D) were determined for 108 staphylococcal isolates. All strains were susceptible (MICs) to daptomycin (< or =2.0 mg/L) and Q-D (< or =1.0 mg/L). All but three isolates were susceptible to vancomycin (< or =4.0 mg/L) and all but one methicillin-resistant Staphylococcus aureus strain were susceptible to linezolid (< or =4.0 mg/L). Q-D had the lowest geometric mean MIC (0.29 mg/L) and daptomycin had the lowest geometric mean MBC (0.57 mg/L). Time-kill tests were performed on 25 isolates. Bactericidal activity (>99.9% kill) was observed with daptomycin at 2 mg/L and at 2 x MBC for 92% of strains tested. In comparison, the bactericidal rates for the other drugs at breakpoint concentrations and at 2 x MBC were 72% and 70% for vancomycin, 46% and 60% for Q-D, and 7% and 14% for linezolid. Of the four drugs tested, daptomycin was bactericidal against the most strains and had the most rapid cidal activity.

Acetamides↗
PubMed2002

Selection of zone size interpretive criteria for disk diffusion susceptibility tests of three antibiotics against Streptococcus pneumoniae, using the New Guidelines of the National Committee for Clinical Laboratory Standards.

Disk diffusion and broth microdilution susceptibility tests were performed with cefotaxime, ceftriaxone, telithromycin, and erythromycin (control) against 407 selected isolates of Streptococcus pneumoniae. Scattergrams were prepared from the results of these tests, and the current NCCLS guidelines for setting disk diffusion test interpretive criteria were applied. Erythromycin zone diameter breakpoints were confirmed. Telithromycin interpretive criteria for the disk test could be easily set with acceptable discrepancy rates. For cefotaxime and ceftriaxone, the minor discrepancy rates for MICs in the intermediate category +/- 1 dilution were far in excess of the acceptable 40% limit, i.e., 52 and 71%, respectively. We conclude that the 30-microg disk of these two drugs cannot be reliably used to test pneumococci.

Anti-Bacterial Agents↗
PubMed2002

Comparative sequence analysis of the symbiosis island of Mesorhizobium loti strain R7A.

The Mesorhizobium loti strain R7A symbiosis island is a 502-kb chromosomally integrated element which transfers to nonsymbiotic mesorhizobia in the environment, converting them to Lotus symbionts. It integrates into a phenylalanine tRNA gene in a process mediated by a P4-type integrase encoded at the left end of the element. We have determined the nucleotide sequence of the island and compared its deduced genetic complement with that reported for the 611-kb putative symbiosis island of M. loti strain MAFF303099. The two islands share 248 kb of DNA, with multiple deletions and insertions of up to 168 kb interrupting highly conserved colinear DNA regions in the two strains. The shared DNA regions contain all the genes likely to be required for Nod factor synthesis, nitrogen fixation, and island transfer. Transfer genes include a trb operon and a cluster of potential tra genes which are also present on the strain MAFF303099 plasmid pMLb. The island lacks plasmid replication genes, suggesting that it is a site-specific conjugative transposon. The R7A island encodes a type IV secretion system with strong similarity to the vir pilus from Agrobacterium tumefaciens that is deleted from MAFF303099, which in turn encodes a type III secretion system not found on the R7A island. The 414 genes on the R7A island also include putative regulatory genes, transport genes, and an array of metabolic genes. Most of the unique hypothetical genes on the R7A island are strain-specific and clustered, suggesting that they may represent other acquired genetic elements rather than symbiotically relevant DNA.

Amino Acids↗
PubMed2002

A genealogy of the social identity tradition: Deleuze and Guattari and social psychology.

This paper explores how social psychology has theorized the relationship between the individual and society. This is done through a genealogical analysis of the Social Identity Tradition (SIT). It is argued that the current state of SIT is profoundly shaped by a range of intellectual and moral strategies derived from the work of Henri Tajfel. This 'Tajfel effect' manifests itself as a way of settling theoretical, practical and moral disputes through the invocation of Tajfel as a founding figure. However, this strategy also ties SIT into a model of the subject and an understanding of society that is increasingly seen as problematic. The paper then goes on to show how a range of core concepts at the heart of SIT may be usefully reformulated by drawing on the work of Deleuze and Guattari. Their work offers SIT a way of thinking about individuals and groups as sites for connection and differentiation. This is illustrated using the example of Nazi social relations that was originally deployed by Tajfel. Potential issues and direction for SIT as reinvigorated by the encounter with Deleuze and Guattari are then sketched out.

Humans↗