Neutron diffraction studies of the 1:1 and 2:1 cocrystals of benzene-1,2,4,5-tetracarboxylic acid and 4,4'-bipyridine.
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Journal Article↗
Biomedical subjects
John A Cowan
Publications and source records attributed to John A Cowan.
Safety belt use by law enforcement officers on reality television: a missed opportunity for injury prevention?
BACKGROUND: Although safety belt usage rates are increasing nationwide, motor vehicle crashes (MVCs) remain a leading cause of death for young people and are emerging as a leading cause for police officers specifically. A content analysis was performed on the television show, COPS, to determine on-air safety belt usage rates. METHODS: A sample of 63 unique episodes of the reality-based television series, COPS, was viewed during a 4-month period (September 1, 2005 to January 1, 2006). Episodes had original airing dates ranging from 1990 to 2004. Safety belt usage status was determined per police officer per driving scene (N = 250). A driving scene represented a continuous trip (start to finish) with a total on-camera time exceeding 5 seconds. Scenes with indeterminate safety belt status were excluded. High-speed driving, officer gender, and officer race were also recorded. RESULTS: Of the 203 scenes included, 77 (38%) demonstrated safety belt usage. High-speed driving scenes had higher safety belt usage rates compared with low-speed (48% versus 29%, p = 0.005). More contemporary episodes (1999 to 2004) had higher safety belt usage rates as well (51% versus 28%, p = 0.001). Officer gender and race revealed no significant differences in safety belt usage rates (p = 0.930 and p = 0.900, respectively). CONCLUSIONS: In this popular, reality-based television series, safety belt usage by police officers is extremely low. These findings suggest the need to increase safety belt usage by police officers, especially those filmed for television.
Accidents, Traffic↗
Epidemiology of aortic aneurysm repair in the United States from 1993 to 2003.
The epidemiology of abdominal aortic aneurysm (AAA) disease has been well described over the preceding 50 years. This disease primarily affects elderly males with smoking, hypertension, and a positive family history contributing to an increased risk of aneurysm formation. The aging population as well as increased screening in high-risk populations has led some to suggest that the incidence of AAAs is increasing. The National Inpatient Sample (1993-2003), a national representative database, was used in this study to determine trends in mortality following AAA repair in the United States. In addition, the impact of the introduction of less invasive endovascular AAA repair was assessed. Overall rates of treated unruptured and ruptured AAAs remained stable (unruptured 12 to 15/100,000; ruptured 1 to 3/100,000). In 2003, 42.7% of unruptured and 8.8% of ruptured AAAs were repaired through an endovascular approach. Inhospital mortality following unruptured AAA repair continues to decline for open repair (5.3% to 4.7%, P = 0.007). Mortality after elective endovascular AAA repair also has statistically decreased (2.1% to 1.0%, P = 0.024) and remains lower than open repair. Mortality rates for ruptured AAAs following repair remain high (open: 46.5% to 40.7%, P = 0.01; endovascular: 40.0% to 35.3%, P = 0.823). These data suggest that the numbers of patients undergoing elective AAA repair have remained relatively stable despite the introduction of less invasive technology. A shift in the treatment paradigm is occurring with a higher percentage of patients subjected to elective endovascular AAA repair compared to open repair. This shift, at least in the short term, appears justified as the mortality in patients undergoing elective endovascular AAA repair is significantly reduced compared to patients undergoing open AAA repair.
Aged↗
Changes in the utilization of spinal fusion in the United States.
OBJECTIVE: Several reports suggest that spine surgery has experienced rapid growth in the past decade. Limited data exist, however, documenting the increase in spinal fusion. The objective of this work was to quantify and characterize the contemporary practice of spinal fusion in the United States. METHODS: Clinical data were obtained from the Nationwide Inpatient Sample for the years from 1993 to 2003. All patients with International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes indicating cervical fusion, thoracolumbar fusion, lumbar or unspecified fusion were identified (n = 471,990). Primary ICD-9-CM diagnosis codes were used to determine the rationale for surgical fusion. Population-based utilization rates overall and for each procedure were calculated from United States census data. Rank order of spinal fusion compared with other inpatient procedures from the Nationwide Inpatient Sample was reported for the years 1997 to 2003. RESULTS: Overall utilization increased during the time period for cervical, thoracolumbar, and lumbar fusions by 89, 31, and 134%, respectively. Patients aged 40 to 59 years experienced the rapid rise in utilization for cervical fusions (60-110 per 100,000) and lumbar fusions (35-84 per 100,000). For patients 60 years and older, utilization also increased for cervical (30-67 per 100,000), thoracolumbar (4-9 per 100,000), and lumbar (42-108 per 100,000). Spinal fusion rose from the 41st most common inpatient procedure in 1997 to the 19th in 2003. CONCLUSION: Cervical, thoracolumbar, and lumbar spinal fusion have experienced a rapid increase in utilization in isolation and compared with other surgical procedures in contemporary practice. These changes are most pronounced for patients over 40 years of age, and degenerative disc disease seems to account for much of this increase.
Adult↗
Variable-temperature neutron diffraction studies of the short, strong hydrogen bonds in the crystal structure of pyridine-3,5-dicarboxylic acid.
Pyridine-3,5-dicarboxylic acid has been studied by single-crystal neutron diffraction at 15 and 296 K. Pyridine-3,5-dicarboxylic acid, in which the carboxylic acid protons have been replaced by deuterons, has also been studied at 15, 150 and 296 K. The protonated structure contains a short N...H...O hydrogen bond [N...O 2.523 (2) Angstrom at 15 K]. Temperature-dependent proton migration occurs where the N--H distance in the hydrogen bond changes from 1.213 (4) Angstrom at 15 K to 1.308 (6) Angstrom at 300 K. In the deuterated structure the overall hydrogen-bond length increased [N...O 2.538 (3) Angstrom at 15 K] and the magnitude of the migration increased so that the N--D distance changes from 1.151 (3) Angstrom at 15 K to 1.457 (4) Angstrom at 300 K.
Journal Article↗
Single-crystal neutron-diffraction study of 3.4% Zn-doped (ND4)2[Cu(D2O)6](SO4)2 at 20 K.
Doping the perdeuterated ammonium copper Tutton salt (ND4)2[Cu(D2O)6](SO4)2 [perdeuterated diammonium hexaaquacopper(II) bis(sulfate)] with Zn leads to a change in the structure from dimorph A (low density) to dimorph B (high density). This change, which accompanies a switch in the direction of the Jahn-Teller distortion, had previously been observed to occur with substitution of Zn2+ at the Cu2+ site of between 1.3 (A) and 3.4% (B). In this study, the single-crystal neutron-diffraction analysis of (ND4)2[(Cu/Zn)(D2O)6](SO4)2 at 20 K, with 3.4% Zn doping and a deuterium substitution of 85% on the H-atom sites, reveals that the structure is entirely of type B, with the Cu/Zn site at an inversion centre and with no evidence of disorder or unusual atomic displacement parameters that might occur near a phase transition boundary.
Journal Article↗
Variation in outcomes after percutaneous coronary intervention in the United States and predictors of periprocedural mortality.
The objective of this study was to characterize variation in mortality rates across hospitals performing percutaneous coronary intervention (PCI) in the United States. For this purpose, data (n = 735,022) from the Nationwide Inpatient Sample from 1996 to 2001 were analyzed. The primary outcome for the analysis was postprocedural in-hospital mortality. Mortality rates were calculated by race, gender, geographic region, comorbid status and hospital volume. There were significant variations in mortality across gender groups, comorbid status, regions and by hospital volume status. Independent predictors of mortality in this large cohort were older age, female gender, lower income and lower hospital volume. The data suggests targets for quality improvement initiatives for patients undergoing PCI particularly in the elderly, females, lower income patients and low volume hospitals. Even in the contemporary era of adjunctive pharmacological therapies and ubiquitous use of stents, hospital volume remains a significant independent predictor of in-hospital mortality.
Age Factors↗
Surgical reversal of prolonged blindness from a metastatic neuroblastoma.
BACKGROUND: Reports of tumor-related anterior visual pathway blindness that have resolved after surgical decompression are rare. The longest reported duration of tumor-related blindness completely reversed by optic nerve decompression is 3 days. We describe a pediatric patient with 7 days of no light perception who experienced reversal of blindness following tumor resection and optic nerve decompression. CASE DESCRIPTION: A 33-month-old boy presented with a 4-day history of no light perception. Magnetic resonance imaging revealed a mass involving the sphenoid sinus, sella turcica, and clivus with significant optic nerve involvement. Loss of light perception and complete absence of a pupillary light reflex were documented for the next 72 h. A sluggish pupillary light reflex was regained 24 h after instituting intravenous steroids. An urgent bi-frontal craniotomy and optic nerve decompression were performed 7 days after the onset of blindness. Surgical pathology revealed metastatic neuroblastoma. Eleven days after optic nerve decompression, the child was able to count fingers and recognize faces and printed book characters. CONCLUSION: Prolonged blindness secondary to tumor-related optic nerve compression may be reversible up to 1 week from onset in children presenting with no light perception.
Blindness↗
The syndrome of hydrocephalus in young and middle-aged adults (SHYMA).
OBJECTIVES: Currently, headache, nausea/vomiting, visual changes, and altered mental status are accepted as indications for the evaluation of hydrocephalus in children; while dementia, gait apraxia, and urinary incontinence remain indications in the elderly. The clinical presentation of hydrocephalus in young and middle-aged adults remains poorly described. Hence, middle-aged patients with mild gait, cognitive, or urinary symptoms unaccompanied by clear exam findings often remain undiagnosed and untreated. METHODS: We report the clinical presentation, treatment, and outcomes of 46 adults (ages 16-55 years) presenting with congenital, acquired, or idiopathic hydrocephalus with imaging-documented ventriculomegaly and elevated CSF pressure. RESULTS: Primary symptoms were related to gait (70%), cognition (70%), urinary urgency (48%), and headaches (56%). Eighty-four percent complained of impaired job performance. The exam findings were subtle or absent (no gait apraxia, minor gait changes in 42.9%, mildly abnormal Mini Mental State exams in only 14.3%, and incontinence in only 3.6%). Twenty-nine patients underwent ventriculoperitoneal (VP) shunting, and 11 endoscopic third ventriculostomy, of whom six subsequently required a VP shunt. Symptomatic improvement was observed in 93% of patients 16+/- 11 months after shunting (56% complete resolution, 37% partial resolution). Patients had been followed for their symptoms an average of 6 years (range, 1-30) prior to diagnosis. DISCUSSION: We propose that there exists a clinically distinct syndrome of hydrocephalus in young and middle-aged adults (SHYMA) that comprises hydrocephalus of all etiologies. SHYMA is characterized by complaints of impaired gait, cognition, bladder control, and headaches, with a discrepancy between the prominence of symptoms and the subtlety of clinical signs. Despite the subtlety of clinical signs, CSF diversion treatment is effective at resolving symptomatology.
Adolescent↗
Structure and bonding of the vanadium(III) hexa-aqua cation. 1. Experimental characterization and ligand-field analysis.
Spectroscopic and crystallographic data are presented for salts containing the [V(OH(2))(6)](3+) cation, providing a rigorous test of the ability of the angular overlap model (AOM) to inter-relate the electronic and molecular structure of integer-spin complexes. High-field multifrequency EPR provides a very precise definition of the ground-state spin-Hamiltonian parameters, while single-crystal absorption measurements enable the energies of excited ligand-field states to be identified. The EPR study of vanadium(III) as an impurity in guanidinium gallium sulfate is particularly instructive, with fine-structure observed attributable to crystallographically distinct [V(OH(2))(6)](3+) cations, hyperfine coupling, and ferroelectric domains. The electronic structure of the complex depends strongly on the mode of coordination of the water molecules to the vanadium(III) cation, as revealed by single-crystal neutron and X-ray diffraction measurements, and is also sensitive to the isotopic abundance. It is shown that the AOM gives a very good account of the change in the electronic structure, as a function of geometric coordinates of the [V(OH(2))(6)](3+) cation. However, the ligand-field analysis is inconsistent with the profiles of electronic transitions between ligand-field terms.
Journal Article↗
Silylene hydride complexes of molybdenum with silicon-hydrogen interactions: neutron structure of (eta(5)-C(5)Me(5))(Me(2)PCH(2)CH(2)PMe(2))Mo(H)(SiEt(2)).
Reduction of CpMoCl(4) with 3.1 equiv of Na/Hg amalgam (1.0% w/w) in the presence of 1 equiv of dmpe and 1 equiv of trimethylphosphine afforded the molybdenum(II) chloride complex Cp(dmpe)(PMe(3))MoCl (1) (Cp = 1,2,3,4,5-pentamethylcyclopentadienyl, dmpe = 1,2-bis(dimethylphosphino)ethane). Alkylation of 1 with PhCH(2)MgCl proceeded in high yield to liberate PMe(3) and give the 18-electron pi-benzyl complex Cp(dmpe)Mo(eta(3)-CH(2)Ph) (2). Variable temperature NMR experiments provided evidence that 2 is in equilibrium with its 16-electron eta(1)-benzyl isomer [Cp(dmpe)Mo(eta(1)-CH(2)Ph)]. This was further supported by reaction of 2 with CO to yield the carbonyl benzyl complex Cp(dmpe)(CO)Mo(eta(1)-CH(2)Ph) (3). Complex 2 was found to react with disubstituted silanes H(2)SiRR' (RR' = Me(2), Et(2), MePh, and Ph(2)) to form toluene and the silylene complexes Cp(dmpe)Mo(H)(SiRR') (4a: RR' = Me(2); 4b: RR' = Et(2); 4c: RR' = MePh; 4d: RR' = Ph(2)). Reactions of 2 with monosubstituted silanes H(3)SiR (R = Ph, Mes, Mes = 2,4,6-trimethylphenyl) produced rare examples of hydrosilylene complexes Cp(dmpe)Mo(H)Si(H)R (5a: R = Ph; 5b: R = Mes; 5c: R = CH(2)Ph). Reactivity of complexes 4a-c and 5a-d is dominated by 1,2-hydride migration from metal to silicon, and these complexes possess H.Si bonding interactions, as supported by spectroscopic and structural data. For example, the J(HSi) coupling constants in these species range in value from 30 to 48 Hz and are larger than would be expected in the absence of H.Si bonding. A neutron diffraction study on a single crystal of diethylsilylene complex 4b unequivocally determined the hydride ligand to be in a bridging position across the molybdenum-silicon bond (Mo-H 1.85(1) A, Si-H 1.68(1) A). The synthesis and reactivity properties of these complexes are described in detail.
Journal Article↗
Synthesis, structure, and reactivity of a dinuclear metal complex with linear M-H-M bonding.
Reaction of two equiv of 1-adamantylzinc bromide with (dippm)NiBr2 (dippm = bis(di-isopropylphosphino)methane) led to a dinuclear metal complex containing a unique linear bridging hydride ligand. The hydride was characterized by neutron diffraction methods, which confirmed a linear bonding mode. Preliminary reactivity studies of this unusual dimer are reported.
Bridged-Ring Compounds↗
Effect of increasing patient age on complication rates following intact abdominal aortic aneurysm repair in the United States.
INTRODUCTION: Advanced age is generally acknowledged as a risk factor for adverse surgical outcomes, but little information exists to define the magnitude of this association from a population-based perspective. This study was undertaken to determine the relation of patient age to complications following abdominal aortic aneurysm (AAA) repair in a population-based experience. METHODS: This study was based upon data from 6397 patients with a primary diagnosis of intact AAA and a procedure code for repair of AAA from the Nationwide Inpatient Sample (NIS) in 2000. The NIS is a 20% stratified random sample representative of all United States hospitals. Primary outcome variables were postoperative complications determined from secondary diagnostic codes. Adjustment for confounding variables was performed using multiple logistic regression. RESULTS: At least one complication affected 29% of patients. Increasing age correlated with a higher risk of having one or more complications (51-60 years, 18.8%; 61-70 years, 27.3%; 71-80 years, 31.2%; >80 years, 34.3%; P < 0.01). Comparison of the oldest to the youngest age group revealed an increased incidence of pulmonary insufficiency (13.9% versus 6.4%), pneumonia (7.7% versus 3.0%), reintubation (9.5% versus 3.9%), acute renal failure (8.8% versus 2.5%), myocardial infarction (4.3% versus 1.6%), and mortality (7.9% versus 1.1%). The association of increasing age to complications and mortality persisted after adjusting for patient case-mix. CONCLUSIONS: Older patient age is independently associated with an increased risk of major postoperative complications after AAA repair. The increasing age of the United States population will compound this healthcare problem. Quality improvement efforts must focus on minimizing complication rates in elderly patients undergoing common vascular surgical procedures including AAA repair.
Age Distribution↗
Hospital teaching status and outcomes of complex surgical procedures in the United States.
HYPOTHESIS: Complex operations performed in teaching hospitals have similar outcomes as those performed in nonteaching hospitals. DESIGN: Observational cohort study with clinical patient data obtained from the Nationwide Inpatient Sample. The Nationwide Inpatient Sample data were linked to the American Hospital Association hospital survey data for 1997 to determine hospital characteristics. Hospitals were considered high volume if they performed more than the median (50th percentile) number of procedures per year. SETTING: Nationally representative sample of hospitals during 1996 and 1997. PATIENTS: Individuals undergoing esophageal resection (n = 1247), hepatic resection (n = 2073), or pancreatic resection (n = 3337) in Nationwide Inpatient Sample hospitals during 1996 and 1997 were included. MAIN OUTCOMES MEASURES: Unadjusted and adjusted in-hospital mortality and prolonged length of stay (>75th percentile). RESULTS: None of the procedures had higher operative mortality rates at teaching hospitals. In unadjusted analyses, pancreatic resection (4.0% vs 8.8%; P<.001), hepatic resection (5.3% vs 8.0%; P =.03), and esophageal resection (7.7% vs 10.2%; P =.10) had lower operative mortality rates at teaching compared with nonteaching hospitals. However, after adjusting for hospital volume in the multivariate analysis, hospital teaching status was no longer a predictor of operative mortality. CONCLUSIONS: Teaching hospitals have lower operative mortality rates for complex surgical procedures. However, the lower mortality rates at teaching hospitals can be explained by higher procedural volume.
Adult↗
Brainstorming about next-generation computer-based documentation: an AMIA clinical working group survey.
UNLABELLED: Computer-based software to record histories, physical exams, and progress or procedure notes, known as computer-based documentation (CBD) software, has been touted as an important addition to the electronic health record. The functionality of CBD systems has remained static over the past 30 years, which may have contributed to the limited adoption of these tools. Early users of this technology, who have tried multiple products, may have insight into important features to be considered in next-generation CBD systems. OBJECTIVE AND METHODS: We conducted a cross-sectional, observational study of the clinical working group membership of the American Medical Informatics Association (AMIA) to generate a set of features that might improve adoption of next-generation systems. The study was conducted online over a 4-month period; 57% of the working group members completed the survey. RESULTS: As anticipated, CBD tool use was higher (53%) in this population than in the US physician offices. The most common methods of data entry employed keyboard and mouse, with agreement that these modalities worked well. Many respondents had experience with pre-printed data collection forms before interacting with a CBD system. Respondents noted that CBD improved their ability to document large amounts of information, allowed timely sharing of information, enhanced patient care, and enhanced medical information with other clinicians (all P < 0.001). Respondents also noted some important but absent features in CBD, including the ability to add images, get help, and generate billing information. CONCLUSIONS: The latest generation of CBD systems is being used successfully by early adopters, who find that these tools confer many advantages over the approaches to documentation that they replaced. These users provide insights that may improve successive generations of CBD tools. Additional surveys of CBD non-users and failed adopters will be necessary to provide other useful insights that can address barriers to the adoption of CBD by less computer literate physicians.
Adult↗
National trends in the use and outcomes of hepatic resection.
BACKGROUND: Hepatic resection is increasingly performed for primary and metastatic tumors. Reports from tertiary care centers show improved outcomes over time with lower operative mortality rates. The objective of this investigation was to characterize trends in the use and outcomes of hepatic resection in the US during a recent 13-year period. STUDY DESIGN: Adult patients with a procedures code for hepatic resection in the Nationwide Inpatient Sample (NIS) from 1988 to 2000 were included. The Nationwide Inpatient Sample is a 20% representative sample of all discharges in the US. Outcomes variables included in-hospital mortality and length of stay. High volume hospitals performed 10 or more (>50th percentile) procedures per year. RESULTS: During the 13-year period, 16,582 patients underwent hepatic resection. The number of procedures performed increased nearly twofold, from 820 per year in 1988 to 1,420 per year in 2000. Similar changes in use were seen for each indication for operation. The overall mortality rate declined from 10.4% (1988 to 1989) to 5.3% (1999 to 2000) during the study period (p < 0.001). The mortality rate was lower at high volume centers than at lower volume centers (5.8% versus 8.9%, p < 0.001), and the decline in mortality over time was greater at high volume centers (10.1% to 3.9%, p < 0.001) compared with to low volume centers (10.6% to 7.4%, p = 0.01). CONCLUSIONS: The number of hepatic resections performed in the US has increased significantly. Short-term outcomes have also improved over the same time period, with more improvement seen at higher volume centers than in lower volume centers.
Adult↗
Diffusion of new technology for the treatment of renovascular hypertension in the United States: surgical revascularization versus catheter-based therapy, 1988-2001.
BACKGROUND: Trends in the management of renovascular hypertension were evaluated by using a representative national database to determine whether a shift in treatment technology and outcomes has occurred. METHODS: Clinical information regarding the treatment of renovascular hypertension in 5433 patients from 1988 to 2001 was derived from the Nationwide Inpatient Sample (NIS) database. Patients were classified into 3 groups: combined aortic and renal revascularization, isolated renal revascularization, and catheter-based procedures (angioplasty with or without stenting). Population-based trends were determined by using sampling weights for each year to estimate the total number of each intervention in the United States. Outcomes were compared using multivariate logistic regression analysis for risk-adjustment. RESULTS: A 73% decrease in combined aortic and renal revascularizations ( P = .033) and a 56% decrease in isolated renal revascularizations ( P < .001) occurred during the study period. Catheter-based procedures have increased 173% from 0.4 to 1.1 procedures per 100,000 adults during this same time period ( P < .001). Predictors favoring catheter-based treatment were admission acuity, increasing age, nonwhite race, and high socioeconomic status. Predictors of mortality for all 3 treatment groups included increasing age, emergent admission, and nonwhite race. CONCLUSIONS: A significant change in the management of patients with renovascular hypertension has occurred, with a shift towards less invasive catheter-based interventions. A better understanding of the diffusion of this technology in the treatment of individuals with renovascular hypertension will influence the training and distribution of future vascular specialists responsible for these patients.
Aged↗
Diffusion of new technology in health care: the case of aorto-iliac occlusive disease.
BACKGROUND: The objective of the current study was to characterize temporal trends in the treatment of aorto-iliac occlusive disease (AIOD) and the impact of the introduction of less invasive therapy on overall intervention rates. METHODS: Patients with diagnostic codes for AIOD, and procedure codes for aortofemoral bypass (AFB) or iliac artery angioplasty and stenting were selected from the Nationwide Inpatient Sample for 1996 to 2000. Utilization rates of both intervention types were determined. Outcome variables including in-hospital mortality and duration of stay were assessed. RESULTS: The rate of iliac artery angioplasty and stenting increased 850%, from 0.4 to 3.4 cases per 100,000 adults (P <.001). The rate of AFB declined 15.5%, from 5.8 to 4.9 cases per 100,000 adults (P <.005). Older age, white race, and higher-income patients were more likely to undergo angioplasty and stenting. AFB had a higher mortality rate, longer duration of stay, and higher hospital charges compared to angioplasty and stenting. CONCLUSIONS: Iliac artery angioplasty and stenting has rapidly gained a large market share in the treatment of AIOD. Acceptable clinical outcomes have likely lowered the threshold for treatment and contributed to the rapid diffusion of this technology for the treatment of AIOD.
Aged↗