bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnesium Sulfate in Labor and Risk of Neonatal Brain Lesions and Cerebral Palsy in Low Birth Weight Infants
Authors: Paneth Nigel , Jetton James , Pinto-Martin Jennifer , Susser Mervyn ,   the Neonatal Brain Hemorrhage Study Analysis Group
Published: August 2004

Objectives. We tested the hypothesis that administration of magnesium sulfate in labor protects against the development of neonatal brain lesions and cerebral palsy (CP) in low birth weight infants.

Methods. Magnesium exposure was ascertained in a population-based cohort of 1105 infants weighing 2000 g or less through review of medical records of maternal magnesium sulfate administration and, where available, elevated maternal serum magnesium levels. Neonatal germinal matrix/intraventricular hemorrhage and parenchymal brain lesions were ascertained by a prospective, timed ultrasound scanning protocol in the first week of life. CP was ascertained at 2 years of age by clinical examination in 80% of survivors and by interview and medical record review in another 6% and was classified as disabling or nondisabling.

Results. No significant reduction in risk of nondisabling CP (adjusted odds ratio [OR], 1.00; 95% confidence interval [CI], 0.53 to 1.88) or disabling CP [DCP] (adjusted OR, 0.63; 95% CI, 0.32 to 1.24) CP with magnesium exposure was found in a logistic regression model that controlled for gestational age, fetal growth, gender, multiple birth status, mode of delivery, amnionitis, and hypertensive disorders. In a small subset of infants, those with onset of parenchymal lesions at 7 days of age or later (n = 29), magnesium exposure was associated with a significantly reduced risk of DCP (OR, 0.10; 95% CI, 0.02 to 0.65). Magnesium sulfate exposure was not associated with germinal matrix/intraventricular hemorrhage (adjusted OR, 0.89; 95% CI, 0.64 to 1.25) or with parenchymal brain lesions (adjusted OR, 0.83; 95% CI, 0.53 to 1.30).

Conclusions. The hypothesis that magnesium sulfate use reduces the risk of neonatal brain lesions or CP in low birth weight infants was not statistically supported in this study, although a modest reduction in risk of DCP cannot be excluded. The data further suggest that magnesium exposure may be associated with reduction in risk of CP in low birth weight infants who have late-onset brain lesions, but this unpredicted observation requires confirmation in another data set. cerebral palsy; magnesium sulfate; infant, low birth weight; preeclampsia; cerebral hemorrhage, infant.
Errors and Correlates in Parental Recall of Child Immunizations: Effects on Vaccination Coverage Estimates
Authors: Suarez Lucina , Simpson Diane M. , Smith David R.
Published: August 2004

Objective. We evaluated the accuracy of parental recall of children’s immunization histories as compared with provider records and examined how errors in parental recall correlate with sociodemographic characteristics.

Design. The validation study was part of a population-based household survey designed to assess immunization levels among Texas children under age 2 years. For 72% (n = 3278), interviewers used vaccination records from the parent to copy dates for the diphtheria and tetanus toxoids and pertussis vaccine (DTP), oral polio vaccine (OPV), and measles, mumps, and rubella (MMR) shots. For parents without shot records (n = 1216), interviewers asked about each vaccine, whether the child had received the shot, how many, and at what age. Of these, 85% (n = 1029) were validated with health provider records.

Results. Measured against provider records, only 34% of parents accurately recalled the number of DTP shots a child had. More often (42%) parents underestimated the number of DTP shots than overestimated (24%). Agreement between parental recall and provider records was high (83%) for the single dose of MMR. Accuracy of parents’ recall did not differ by race/ethnicity, education level, or type of health insurance coverage, but decreased as child’s age increased. Having a vaccination record at home was associated with a higher immunization status. Hispanic, lower educated, and uninsured parents were more likely to have a vaccination record than non-Hispanic, higher educated, and privately insured parents.

Discussion. Validity of parental recall of children’s immunization histories depends on the vaccine and the age of the child, which is highly correlated with the number of shots parents must recollect. Results suggest that inclusion of parent recall information from vaccination surveys underestimates DTP:OPV:MMR coverage. This underestimation is consistent across economic and race/ethnic groups. Thus, community surveys based on cards and recall should provide reliable conclusions about which groups need intensive program efforts. For the routine monitoring of vaccination coverage, reasonable estimates can be obtained by combining parent-held record and parent recall data. Caution is required when comparing coverage estimates from different surveys since the source of information and method of derivation will produce widely varying coverage rates. vaccinations, immunization, validity, recall bias, infant.
Socioeconomic Variation in Discretionary and Mandatory Hospitalization of Infants: An Ecologic Analysis
Authors: McConnochie Kenneth M. , Roghmann Klaus J. , Liptak Gregory S.
Published: August 2004

Objectives. To examine geographic variation in rates of infant hospitalization for diagnoses classified by type of hospitalization decision in Monroe County (Rochester), New York.

Methods. Study design was cross-sectional and ecologic.International Classification of Diseases (ICD) codes were used to categorize all 7883 hospitalizations for infants (age, <24 months) beyond the newborn period between 1985 and 1991. Postal zip codes defined socioeconomic areas as inner-city, other urban, and suburban for the population at risk. In 1990, inner-city infants included 62% black and 65% Medicaid-covered infants, whereas suburban infants included 3% black and 6% covered by Medicaid. Hospitalization rates were compared among the three socioeconomic areas.

Results. Overall hospitalization rate was 50.3 per 1000 child years. Admissions classified as discretionary accounted for 59% of these, followed by those classified as mandatory, 18%; sometime (congenital heart disease, cleft palate), 15%; discretionary surgery (inguinal hernia, tonsillectomy/adenoidectomy), 6%; and unlikely to need admission, 2%. A stepwise, socioeconomic gradient in hospitalization was found, with rates of 38.1, 51.3, and 82.9 per 1000 child-years, respectively, for suburban, other urban, and inner-city areas. Rates for discretionary, unlikely, and mandatory admissions followed this gradient. Using the odds for hospitalization of suburban infants as the base odds, the odds ratio for discretionary hospitalization for inner-city infants was 2.88 (95% confidence interval [CI], 2.69 to 3.08) and that for mandatory hospitalization was 2.20 (95% CI, 1.94 to 2.49). In multiple regression analysis, low education level of mothers explained 81% of the variance in discretionary hospitalization rate. Although the per capita rate of hospital care of inner-city infants was more than twofold greater than that for suburban infants, potential for reducing this difference is suggested by the fact that discretionary admissions accounted for 78.9% of this difference, whereas mandatory admissions accounted for 17.7% of the difference.

Conclusion. The hospitalization rate for inner-city infants is much greater than that for suburban infants. A substantial portion of the difference, namely that attributable to mandatory admissions, reflected higher rates of serious illness. Differences attributable to discretionary admissions may reflect higher rates of serious illness to some extent, but also appear to reflect less effective health services to a substantial degree.
Impact of Zinc Supplementation on Morbidity From Diarrhea and Respiratory Infections Among Rural Guatemalan Children
Authors: Ruel Marie T. , Rivera Juan A. , Santizo Maria-Claudia , Lönnerdal Bo , Brown Kenneth H.
Published: August 2004

Objective. A community-based, randomized, double-blind intervention trial was conducted to measure the impact of zinc supplementation on young Guatemalan children's morbidity from diarrhea and respiratory infections.

Methods. Children aged 6 to 9 months were randomly assigned to receive 4 mL of a beverage containing 10 mg of zinc (as zinc sulfate) daily (7 d/wk) for 7 months (n = 45) or a placebo (n = 44). Morbidity data were collected daily. Diagnoses of diarrhea, fever, and anorexia were based on mothers' definitions. Respiratory infections were defined as the presence of at least two of the following symptoms: runny nose, cough, wheezing, difficulty breathing, or fever.

Results. High rates of diarrhea and respiratory infections were reported. Children from the placebo group had a 20% episodic prevalence of diarrhea, with 8 episodes/100 d, and a 7% episodic prevalence of respiratory infections, with 3 episodes/100 d. The median incidence of diarrhea among children who received zinc supplementation was reduced by 22% (Wilcoxon rank test), with larger reductions among boys and among children with weight-for-length at baseline lower than the median of the sample (39% reductions in both subgroups). Zinc supplementation also produced a 67% reduction in the percentage of children who had one or more episodes of persistent diarrhea (χ2 test). No significant effects were found on the episodic prevalence of diarrhea, the number of days per episode, or the episodic prevalence or incidence of respiratory infections.

Conclusions. The large impact of zinc supplementation on diarrhea incidence suggests that young, rural Guatemalan children may be zinc deficient and that zinc supplementation may be an effective intervention to improve their health and growth.
Effect of Diuretics on Urinary Oxalate, Calcium, and Sodium Excretion in Very Low Birth Weight Infants
Authors: Campfield Thomas , Braden Gregory , Flynn-Valone Patrecia , Powell Steven
Published: August 2004

Objective. To study the effect of diuretic drugs on urinary oxalate excretion in premature infants, and to examine the relationship between urinary calcium and sodium excretion in premature infants.

Methodology. We measured urinary oxalate, calcium, and sodium excretion in 32 premature infants at approximately 34 weeks gestational age. Seven infants were receiving furosemide, 5 infants were receiving thiazide, 8 infants were receiving furosemide plus thiazide, and 12 infants who were not receiving diuretics served as controls.

Results. Urinary oxalate to creatinine ratios in infants receiving furosemide (0.48 ± .26), thiazide (0.54 ± .20), furosemide plus thiazide (0.44 ± .19), and control infants (0.51 ± .43) were similar by analysis of variance (ANOVA). Data expressed as oxalate concentration gave similar results. Urinary calcium to creatinine ratios in infants receiving furosemide (0.81 ± .30), thiazide (0.54 ± .25), furosemide plus thiazide (0.75 ± .49), and control infants (0.37 ± .25) were similar by ANOVA. The urinary calcium concentration in infants receiving furosemide plus thiazide (0.085 ± 0.042 mg/mL) was different from control infants (0.044 ± .023) by ANOVA and Student-Newman-Keuls test. Urinary calcium to creatinine ratio was correlated with sodium to creatinine ratio (r = .751).

Conclusion. Urinary oxalate excretion in premature infants is not affected by diuretic drugs. Urinary sodium and calcium excretion are closely linked in sodium supplemented premature infants receiving diuretics. The calciuric effect of furosemide is not decreased by the addition of thiazide in premature infants receiving sodium supplements.
Simplified Treatment of Acute Staphylococcal Osteomyelitis of Childhood
Authors: Peltola Heikki , Unkila-Kallio Leila , Kallio Markku J.T. ,   the Finnish Study Group
Published: August 2004

Objective. Recommendations on treatment of acute staphylococcal osteomyelitis of children, based mostly on retrospective analyses, comprise surgical drainage, up to 6 weeks of antimicrobials guided by the erythrocyte sedimentation rate, and the possibility of switching to the oral route only if monitoring of serum bactericidal titer is guaranteed. A prospective study was conducted to test whether the treatment could be simplified.

Design. Fifty pediatric cases of acuteStaphylococcus aureus osteomyelitis were randomized to receive 150 mg/kg/day of cephradine divided in four doses, or 40 mg/kg/day in four doses of clindamycin. The treatment was initiated intravenously, but switched to oral administration mostly within 4 days, using the same doses. The peak antimicrobial serum inhibitory titer or bactericidal titer was not measured. The course of illness was monitored by blood leukocytes, erythrocyte sedimentation rate, and serum C-reactive protein. The follow-up was extended to 1 year posthospitalization.

Setting. Eight tertiary pediatric-orthopedic hospitals in Finland.

Main Outcome Measure. Full recovery and remaining healthy at least 12 months from hospital discharge.

Results. The lower and upper extremities were affected in 72% and 8% of patients, respectively. No surgery at all or needle aspiration only was performed in 62% and drilling in 38%. C-reactive protein and the sedimentation rate normalized within 9 days and 29 days, respectively. X-ray changes developed in 68% but had no prognostic significance. The mean hospitalization time was 11 days, and the total duration of antimicrobials was 23 days. No failure has occurred nor have long-term sequelae been observed in any patient.

Conclusions. Treatment of pediatric acute staphylococcal osteomyelitis can be simplified and costs reduced by keeping surgery at a minimum, shortening hospitalization and the course of antimicrobials, switching quickly to the oral route, and not monitoring serum bactericidal activity.
Use of Codeine- and Dextromethorphan-Containing Cough Remedies in Children
Authors:   Committee on Drugs
Published: August 2004

Numerous prescription and nonprescription medications are currently available for suppression of cough, a common symptom in children. Because adverse effects and overdosage associated with the administration of cough and cold preparations in children have been reported, education of patients and parents about the lack of proven antitussive effects and the potential risks of these products is needed.
Lipoprotein (a): Its Role in Childhood Thromboembolism
Authors: Nowak-Göttl Ulrike , Debus Ottfried , Findeisen Martina , Kassenböhmer Reiner , Koch Hans Georg , Pollmann Harmut , Postler Christiane , Weber Peter , Vielhaber Heinrich
Published: August 2004

Purpose. Elevated lipoprotein (a) [LP (a)] concentrations are independent risk factors of coronary heart disease or stroke in young adults. To clarify its role in childhood thromboembolism, Lp (a) was measured in 72 children with thromboembolism.

Methods. In addition to Lp (a), defects of the protein C anticoagulant system, antithrombin, and antiphospholipid antibodies were investigated in children with arterial (n = 36) or venous (n = 36) thrombosis.

Results. Enhanced Lp (a) >50 mg/dL was diagnosed in 8 out of 36 children with arterial and 5 out of 36 patients with venous thrombosis. Of the 72 children, 25 showed the factor V Leiden mutation, 10 showed protein C deficiency, 2 showed antithrombin deficiency, and 4 showed primary antiphospholipid syndrome. Three children with increased Lp (a) were heterozygous for the factor V Leiden mutation, and 1 girl showed additional protein C deficiency.

Conclusions. Data of this study indicate that increased concentrations of Lp (a) play an important role in childhood thrombosis. childhood thrombosis, lipoprotein (a), factor V Leiden, protein C.
Universal Newborn Hearing Screenings: A Three-Year Experience
Authors: Barsky-Firkser Lisa , Sun Shyan
Published: August 2004

Objective. To perform hearing screenings on all newborns before hospital discharge, using auditory brainstem evoked responses with analysis of time, cost, and failure rates to evaluate and determine the screening practicality.

Method. Over a 3-year period from January 1, 1993 to December 31, 1995, auditory brainstem evoked response screenings were performed on 15 749 infants born at Saint Barnabas Medical Center, Livingston, New Jersey, before their hospital discharge by certified/licensed audiologists. The auditory brainstem evoked response screenings were conducted using the Nicolet Compass Evoked Potential System.

Results. A 3-year experience of testing 15 749 infants proved to be a cost-effective program with costs less than $30.00/baby. To date, 46 babies have been identified with bilateral sensorineural hearing loss and 6 babies with unilateral sensorineural hearing loss.

Conclusions. The universal newborn hearing screening program at Saint Barnabas Medical Center has proved to be effective, beneficial, and necessary for an institution with more than 5000 births, annually. Early identification of hearing loss has resulted in infants receiving early intervention, and the screening program has provided education and follow-up services to both parents and physicians. auditory brainstem evoked responses, early hospital discharge of newborns, early identification of hearing loss, screening auditory brainstem evoked responses, universal newborn hearing screening.
Parents’ and Physicians’ Views on Antibiotics
Authors: Palmer Diana A. , Bauchner Howard
Published: August 2004

Objective. To describe parents’ opinions and concerns about antibiotics and to contrast these opinions with those of pediatricians.

Design. Parents were surveyed using an interviewer-administered questionnaire and pediatricians were mailed a self-administered questionnaire.

Results. Parents from two private practices (N = 300) were largely white (84%) and had completed college (81%). The parents from a community health center (N = 100) were mostly black (80%) and had not completed college (91%). Twenty-nine percent of parents were worried that their children were receiving too many antibiotics. Eighty-five percent believed there were problems with receiving too many antibiotics, with 55% mentioning resistance or immunity as concerns. Eighteen percent of parents had given their child an antibiotic at home before consulting a physician. Parents believed that antibiotics were always or sometimes required for ear infections (93%), throat infections (83%), colds (32%), cough (58%), and fever (58%). Fourteen percent of parents believed that their child had required an antibiotic when the doctor did not prescribe one, with clinic parents significantly more likely to report this issue (22%) than private practice parents (12%). Nine percent believed that their doctor had prescribed an antibiotic unnecessarily (private practice = 12%, community health center = 3%). Parents from the private practices were also more likely to report requesting a specific antibiotic (34%) in comparison with 19% of clinic parents.

Sixty-one percent of the physician surveys were returned after two mailings and a follow-up phone call. The pediatricians had been in practice for a median of 12 years, seeing a median of 110 patients per week. Fifty-eight percent of pediatricians reported that some, many, or most of the parents in their practices were worried that their children were receiving too many antibiotics. Seventy-one percent indicated that four or more times during the previous month, a parent had requested an antibiotic when the physician believed it was unnecessary, and 35% said that at least occasionally they went along with these requests. Sixty-one percent reported that parents requested a different antibiotic from the one they were going to prescribe at least four times in the previous month, and 30% of pediatricians said that they agreed to parents’ requests often or most of the time.

Conclusions. Both the parent and the physician surveys suggest that parents are concerned about the overuse of antibiotics, but often request them when their physicians believe they are unnecessary. Parents often administer antibiotics without physician knowledge, and many parents have misconceptions about which illnesses warrant antibiotic therapy. Understanding parents’ concerns and beliefs about antibiotics and the range of physician practice styles with respect to antibiotics may direct the development of intervention strategies to reduce the inappropriate use of oral antibiotics. antibiotics, parents, pediatricians, resistance.
A Randomized Controlled Trial of Group Versus Individual Well Child Care for High-risk Children: Maternal-Child Interaction and Developmental Outcomes
Authors: Taylor James A. , Davis Robert L. , Kemper Kathi J.
Published: August 2004

Objective. To determine if group well child care (GWCC) for high-risk children affects maternal-child interaction and development as compared to these outcomes in children receiving traditional individual well child care (IWCC).

Study Design. Randomized controlled trial.

Participants. Infants less than 4 months old at the initiation of the study who came from high-risk families. Families were classified as high risk, and eligible for study participation, if the mother had one or more of the following characteristics: poverty, single marital status, less than a high school education, age less than 20 years at delivery, previous substance abuse, or a history of abuse as a child.

Setting. Two urban, university pediatric clinics in Seattle, Washington.

Interventions. Study children were randomized to receive GWCC or IWCC prior to the first study visit at the age of 4 months. Study health supervision visits were scheduled at 4, 5, 6, 8, 10, 12, and 15 months of age. For children randomized to receive GWCC, study visits consisted of an age-matched group discussion of child rearing issues, either preceding or following a brief physical examination. After the 15-month visit, development of study patients was assessed by the use of Bayley Scales of Infant Development (Bayley). Maternal-child interaction and the home environment were evaluated by the use of the Nursing Child Assessment Teaching Scale (NCATS) and the Home Observation for Measurement of the Environment (HOME), respectively.

Results. At least one outcome measure was obtained on 114 children; 86 patients completed all three outcome measures. Bayley psychomotor mean scores were 103.6 ± 11.5 for GWCC patients versus 100.0 ± 12.4 for those receiving IWCC (P= .14); mean scores for the mental section were 99.3 ± 14.8 and 100.4 ± 14.3, respectively (P = .71). The prevalence of high-risk maternal-child interactions was 10% in both the GWCC and IWCC groups. A high-risk home environment was found in 16% of IWCC patients versus 4% of those randomized to GWCC (odds ratio comparing IWCC to GWCC 4.6, 95% confidence interval 0.78, 26.0, after controlling for confounding variables). Provider time was similar among groups (mean number of minutes/patient/study visit: 19.8 ± 5.6 and 20.4 ± 6.7 for GWCC and IWCC, respectively,P = .66).

Conclusion. GWCC is a viable alternative to IWCC for high-risk children. Developmental outcomes and maternal-child interaction are at least as good for children who received GWCC as compared to traditional IWCC, without any increase in provider time required. well child care, child development, maternal-child interaction, Bayley Scales of Infant Development, Nursing Child Assessment Teaching Scale, Home Observation for Measurement of the Environment.
Clinical aspects and conservative management of placenta accreta
Authors: Armstrong Charles A , Harding Steven , Dickinson Jan E
Published: August 2004

Placenta accreta is a rare complication of human placentation with fertility and life‐threatening sequelae. Traditional management has centred upon hysterectomy and its prompt undertaking has been well documented in saving lives. While in many situations hysterectomy will remain appropriate, there are other management options available involving conservative approaches. This article reviews the diagnosis and demographics of this potentially frightening pathology and highlights the important aspects of conservative management if hysterectomy is to be avoided.
Pelvic inflammatory disease
Authors: Mears Alison , Bingham James S
Published: August 2004

Pelvic inflammatory disease is a common but often uncertain diagnosis, crossing the specialty boundaries of general practice, family planning, accident and emergency medicine, genitourinary medicine and gynaecology. As well as the immediate morbidity it causes, it can commonly lead to potentially serious complications (subfertility, ectopic pregnancy, chronic pelvic pain and psychological morbidity). Despite a number of published guidelines, uncertainty and variation still surround its diagnosis, clinical management and treatment. In this article, we review current guidelines and literature and highlight recent developments and controversies.
Cationic Transition Metal Arene Interactions
Authors: Diefenbach Martin , Schwarz Helmut
Published: August 2004

Describing selected examples, this contribution aims at discussing structural, electronic, and thermochemical aspects of cationic transition metal–arene complexes in gas‐phase chemistry. The main focus is cast on the application of quantum chemistry to metal–benzene complexes and derivatives and on a comparison to experiment where appropriate. The reader is taken through an overview starting from general electronic and molecular orbital considerations and leading to structural and thermochemical implications thereof. A short section on transition metal–arene reactivity and a final paragraph on miscellaneous related systems conclude the article.
The Current State of Electronic Publishing of Scientific Manuscripts
Authors: Heller Stephen R. , Bachrach Steven M.
Published: August 2004

This presentation surveys the area of electronic manuscript publishing with an emphasis on how XML, CML, and the INChI activities are having and will continue to have a major impact on scientific publishing.
Entropy from Quantum Chemical Computations
Authors: East Allan L. L.
Published: August 2004

This article describes the computation of the third‐law gas‐phase entropy of a molecule. Formulae from statistical thermodynamics are used, on the basis of canonical partition functions and relying on molecular parameters determinedab initio.Sensitivity of computed entropies to theab initioaccuracy of molecular parameter values will be discussed. Special discussion is devoted to approximations dealing with multiple minima of fluxional molecules, particularly rotational conformers connected by internal rotation.
Computational Prediction of Intestinal Absorption
Authors: Clark David E.
Published: August 2004

This review covers thein silicoprediction of human intestinal permeability, fraction absorbed in humans, and Caco‐2 permeability, particularly focusing on recent developments and the current state of the art. It is suggested that the largest obstacle in the way of the development of improved predictive models is the current lack of suitable experimental data sets. Some likely future developments are outlined: notably the use of consensus models, the integration of absorption models with models for other absorption‐related processes, and the inclusion of better confidence estimates in the output of predictive models.
Absorption
Authors: von Stockar Urs , Wilke Charles R.
Published: August 2004

Absorption, or gas absorption, is a unit operation used in the chemical industry to separate gases by washing or scrubbing a gas mixture with a suitable liquid. One or more of the constituents of the gas mixture dissolves or is absorbed in the liquid and can thus be removed from the mixture. In some systems, this gaseous constituent forms a physical solution with the liquid or the solvent, and in other cases, it reacts with the liquid chemically. The purpose of such scrubbing operations may be gas purification, eg, removal of air pollutants from exhaust gases; product recovery; or production of solutions of gases for various purposes. Gas absorption is usually carried out in vertical countercurrent columns. The solvent is fed in at the top of the absorber, the gas mixture from the bottom. The absorbed substance is washed out by the solvent, which is often recovered in a subsequent
stripping
or desorption operation. The absorber may be a packed column, plate tower, or simple spray column, or a bubble column. The fundamental physical principles underlying the process of gas absorption are the solubility of the absorbed gas and the rate of mass transfer. Information on both must be available when sizing equipment for a given application. In standard packed absorption columns, a gas mixture travels up through a gas absorption tower and the solute is transferred to the liquid phase and thus gradually removed from the gas. The liquid accumulates solute on its way down through the column. Multicomponent mass‐transfer effects, nonisothermal gas absorption, and axial dispersion effects result in considerable departures from ideal flow assumptions. Neglect of axial dispersion results in an overestimation of the driving forces and may lead to an unsafe design. Bubble tray absorption columns may be designed graphically based on a so‐called McCabe‐Thiele diagram. The required number of actual plates, however, is larger than the number of theoretical plates. The computation of nonisothermal gas absorption processes is difficult because of all the interactions involved. A computer is normally required to establish the correct concentration and temperature profiles through the tower.
Acetylene, Properties and Manufacturing from Calcium Carbide
Authors: Manyik Robert M. , Dietz C. M. , Sargent H. B. , Thribolet R. O. , Schaffer R. P.
Published: August 2004

Acetylene, C2H2, is a highly reactive, commercially important hydrocarbon. Its reactivity is related to its triple bond between carbon atoms and, as a consequence, its high positive free energy of formation. Because of its explosive nature, long distance shipping or pressurized storage is not recommended. Thus acetylene is generally used as it is produced without shipping or storage.

Commercially, acetylene is used primarily as a raw material for the synthesis of a variety of organic chemicals. In the United States, this accounts for about 80% of acetylene usage, with the balance being used for metal welding and cutting. Worldwide acetylene production peaked in the mid‐1960s, after which it declined dramatically as processes were developed to substitute lower cost olefins and paraffins for the acetylene feedstock. Production levels reached a minimum in the early 1980s and since have been growing at a rate of about 2–4% per year, mainly in response to the growth of 1,4‐butanediol production.

Although acetylene production in Japan, China, and Eastern Europe is still based on the calcium carbide process, the large producers in the United States, Western Europe, and Russia now rely principally on the partial oxidation of natural gas. However, much of the incremental growth in production is based on producing acetylene as a coproduct of ethylene in the steam cracking process. As a coproduct, acetylene is much less costly than as produced from partial oxidation or calcium carbide.
Acetyl Chloride
Authors: Wagner Frank S.
Published: August 2004

Acetyl chloride, C
2
H
3
OCl, mol wt 78.50, is a colorless, corrosive, irritating liquid that fumes in air. It reacts very rapidly with water, readily hydrolyzing to acetic acid and hydrochloric acid. Acetyl chloride is toxic. Its high reactivity leads to modifications that block the action of enzymes needed by living tissue. Acetyl chloride is manufactured by the reaction of sodium acetate or acetic acid and phosphorus trichloride. It is a powerful acetylating agent and is used in the manufacture of aspirin, acetaminophen, acetanilide, and acetophenone, and in liquid crystal compositions.
Acrolein and Derivatives
Authors: Etzkorn W. G. , Kurland J. J. , Neilsen W. D.
Published: August 2004

Acrolein (2‐propenal), C
3
H
4
O, is the simplest unsaturated aldehyde

\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{(}{\rm{CH}}{_{2}}{\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}}{\rm{CHCHO}}{)}}$\end{document}

. The primary characteristic of acrolein is its high reactivity due to conjugation of the carbonyl group with a vinyl group. More than 80% of the refined acrolein that is produced today goes into the synthesis of methionine. Much larger quantities of crude acrolein are produced as an intermediate in the production of acrylic acid. Acrolein is a highly toxic material with extreme lacrimatory properties. Special care in handling is required because of its flammability, reactivity, and toxicity. Acrolein is highly reactive in a variety of reactions, including oxidation and reduction and in reactions with alcohols. Because of its antimicrobial activity, it has found use as an agent to control the growth of microbes in process feed lines.
Acrylamide
Authors: Habermann C. E.
Published: August 2004

Acrylamide (NIOSH No. A533250) has shown steady growth since the mid‐1950s, but is still considered a small‐volume commodity. It is by far the most important member of the series of acrylic and methacrylic amides. Water‐soluble polyacrylamides have the most important applications, including potentially large uses in enhanced oil recovery as mobility‐control agents in water flooding, additives for oilwell drilling fluids, and aids in fracturing and acidifying. Acrylamide, C3H5NO, is a difunctional monomer containing a reactive electron‐deficient double bond and an amide group. It undergoes reactions typical of those two functionalities. The current routes to acrylamide are based on the hydration of inexpensive and readily available acrylonitrile. Contact with acrylamide can be hazardous and should be avoided.
Adipic Acid
Authors: Davis Darwin D. , Kemp Donald R.
Published: August 2004

Adipic acid, hexanedioic acid, 1,4‐butanedicarboxylic acid, mol wt 146.14, HOOCCH2CH2CH2CH2COOH, is a white crystalline solid with a melting point of about 152°C. Little of this dicarboxylic acid occurs naturally, but it is produced on a very large scale at several locations around the world. The majority of this material is used in the manufacture of nylon‐6,6 polyamide, which is prepared by reaction with 1,6‐hexanediamine. Adipic acid is a colorless, odorless, sour‐tasting crystalline solid that undergoes reactions including esterification, amidation, reduction, halogenation, salt formation, and dehydration. It also undergoes several industrially significant polymerization reactions. Adipic acid historically has been manufactured predominantly from cyclohexane. During the 1970s and 1980s, however, much research has been directed to alternative feedstocks, especially butadiene and cyclohexene, as dictated by shifts in hydrocarbon markets. Growing concern with air quality may exert further pressure for alternative routes as manufacturers seek to avoid NOxabatement costs. When dispersed as a dust, adipic acid is subject to normal dust explosion hazards. The material is an irritant, especially upon contact with the mucous membranes. Protective goggles or face shields should be worn when handling the material. The material should be stored in corrosion‐resistant containers, away from alkaline or strong oxidizing materials. Adipic acid is a very large‐volume organic chemical and is one of the top 50 chemicals produced in the United States in terms of volume, although demand is highly cyclic. Adipic acid for nylon takes about 60% of U.S. cyclohexane production. Adipic acid is relatively nontoxic.
Adsorption, Liquid Separation
Authors: Gembicki Stanley A. , Oroskar Anil R. , Johnson James A.
Published: August 2004

Liquid‐phase adsorption has long been used for the removal of contaminants present at low concentrations in process streams. In most cases, the objective is to remove a specific feed component; alternatively, the contaminants are not well defined, and the objective is the improvement of feed quality defined by color, taste, odor, and storage stability. In contrast to trace impurity removal, the use of adsorption for bulk separation in the liquid phase on a commercial scale is a relatively recent development; this article is devoted mainly these liquid‐phase bulk adsorptive separation processes. A significant advantage of adsorbents over other separative agents lies in the fact that favorable equilibrium‐phase relations can be developed for particular separations; adsorbents can be produced that are much more selective in their affinity for various substances than are any known solvents. A practical adsorbent has four primary requirements: selectivity, capacity, mass transfer rate, and long‐term stability. The requirement for adequate adsorptive capacity restricts the choice of adsorbents to microporous solids with pore diameters ranging from a few tenths to a few tens of nanometers. Zeolites, crystalline aluminosilicates containing an assemblage of SiO4and AlO4tetrahedra joined together by oxygen atoms to form a microporous solid, offer increased possibilities for exploiting molecular‐level differences among adsorbates. The versatility of zeolites lies in the fact that widely different adsorptive properties may be realized by the appropriate control of the framework structure, the silica‐to‐alumina ratio (Si/Al), and the cation form. Industrial‐scale adsorption processes can be classified as batch or continuous. The efficiency of an adsorption process is significantly higher in a continuous mode of operation than in a cyclic batch mode. In addition, in a batch mode, the four functions of adsorption, purification, desorption, and displacement of the desorbent from the adsorbent are inflexibly linked, whereas a continuous mode allows more degrees of freedom with respect to these functions, and thus a better overall operation. Continuous processes have wide application in different areas of the chemical industry. However, in some applications the cyclic‐batch process may be preferred because of the complexity of design and the difficulty of controlling the continuous processes. Examples of commercial cyclic‐batch adsorption processes include the UOP methanol recovery (UOP MRU) and oxygenate removal (UOP ORU) processes. Conventional liquid chromatography has not attained great commercial significance in the area of large‐scale bulk separations from the liquid phase. Liquid adsorption processes hold a prominent position in several applications for the production of high purity chemicals on a commodity scale, and they continue to increase in value as improvements are made.
Aerosols
Authors: Sciarra John J.
Published: August 2004

The aerosol container has enjoyed commercial success in a wide variety of product categories. Insecticide aerosols were introduced in the late 1940s, and shave foams, hair sprays, deodorants, paints, perfumes, whipped cream, and automotive products followed in the 1950s. Medicinal metered‐dose aerosol products have also been developed for use in the treatment of asthma, migraine headaches, and angina. Personal products are the fastest growing segment of the aerosol industry and represent the largest of the categories. Aerosol products are hermetically sealed, ensuring that the contents cannot leak, spill, or be contaminated. The packages can be considered to be tamper‐proof. They deliver the product in an efficient manner, generating little waste, often to sites of difficult access. By control of particle size, spray pattern, and volume delivered per second, the product can be applied directly without contact by the user. All aerosols consist of product concentrate, propellant, container, and valve (including an actuator and dip tube). The propellant, said to be the heart of an aerosol system, maintains a suitable pressure within the container and expels the product once the valve is opened. Propellants may be either a liquefied halocarbon, hydrocarbon, or halocarbon–hydrocarbon blend, or a compressed gas such as carbon dioxide, nitrogen, or nitrous oxide. Worldwide, use of CFC propellants, designated as Propellants 11, 12, and 114, is strictly limited to specialized medicinal aerosol products such as metered‐dose inhalers. The most popular aerosol container is the three‐piece, tin‐plated steel container. All aerosols are produced by either a cold‐filling or pressure‐filling process. Barrier packs utilize a plastic bag or piston to separate the product from the propellant.
Air Pollution
Authors: Wolff George T.
Published: August 2004

Air pollution is the presence of any substance in the atmosphere at a concentration high enough to produce an objectionable effect on humans, animals, vegetation, or materials, or to significantly alter the natural balance of any ecosystem. Substances can be solids, liquids, or gases, and can be produced by anthropogenic activities or natural sources. In this article only nonbiological material is considered and the discussion of airborne radioactive contaminants is limited to radon. The original six criteria pollutants, for which the Environmental Protection Agency is required to summarize published information on each, were sulfur dioxide, SO2; carbon monoxide, CO; nitrogen dioxide, NO2; ozone, O3; suspended particulates; and nonmethane hydrocarbons, NMHC. The NMHC are now referred to as volatile organic compounds (VOC). The NMHC were dropped from the list shortly after the criteria pollutants were so designated. In the late 1970s, lead, Pb, was added to the list and in 1987, so was particulate matter having an aerodynamic diameter of less than or equal to 10 µm, PM10. There have been several developments since the establishment of the criteria pollutants. In the mid‐1970s it was shown that high concentrations of O3and sulfate haze could be transported hundreds of miles, and acid deposition studies in the 1980s clearly illustrated the international and global aspects of this transport. Then stratospheric O3depletion and global warming became issues and air pollution was finally viewed in a global context. Air pollution can be considered to have three components: sources, transport and transformations in the atmosphere, and receptors. The source emits airborne substances. The receptor is the person, animal, plant, material, or ecosystem affected by the emissions. In the United States, the framework for air quality management is the Clean Air Act (CAA), which defines two categories of pollutants; criteria and hazardous. For the criteria pollutants, the CAA requires that EPA establish National Ambient Air Quality Standards (NAAQS) and emissions standards for stationary sources and for motor vehicles. For the hazardous air pollutants, only emissions standards for some sources are required, but the number is growing rapidly. Current air pollution concerns include photochemical smog, volatile organic compounds (VOC), nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), particulate matter, global warming (the greenhouse effect), and stratospheric O3depletion, among others.
Aldehydes
Authors: Miller David J.
Published: August 2004

Aldehydes are carbonyl‐containing organic compounds in which the carbonyl function is at a terminal carbon. These compounds are extremely reactive. The carbonyl group is susceptible to both oxidation and reduction, yielding acids and alcohols, respectively. The common method of naming aldehydes corresponds very closely to that of the related acids in that the termaldehydeis added to the base name of the acid. The C‐1 and C‐2 carbon aliphatic aldehydes, formaldehyde and acetaldehyde, are gases at ambient conditions whereas the C‐3 (propanal) through C‐11 (undecanal) aldehydes are liquids, and higher aldehydes are solids at room temperature. The lower, C‐1 to C‐8 aldehydes have pungent, penetrating, unpleasant odors. Above C8, aldehydes have more pleasant odors and some higher aldehydes are used in the perfume and flavoring industries. Reactions of aldehydes generally fall into two classes: those directly affecting the carbonyl group and those involving the adjacent carbon atom. There are, acute effects of aldehydes: eye, skin, and respiratory tract irritation and organ pathology. Aldehydes find the most widespread use as chemical intermediates. A large proportion of aldehydes are converted to alcohols for use as solvents and in the manufacture of plasticizers. Fatty aldehydes C‐8–C‐13 are used in nearly all perfume types and aromas.
Alkanolamines from Nitro Alcohols
Authors: Bollmeier Allen F.
Published: August 2004

The nitro alcohols obtained by the condensation of nitroparaffins with formaldehyde may be reduced to a unique series of alkanolamines (β‐amino alcohols). The five primary amino alcohols manufactured on a commercially significant scale are 2‐amino‐2‐methyl‐1‐propanol (AMP), 2‐amino‐2‐ethyl‐1,3‐propanediol (AEPD), 2‐amino‐2‐(hydroxymethyl)‐1,3‐propanediol (TRIS AMINO), 2‐amino‐2‐methyl‐1,3‐propanediol (AMPD), and 2‐amino‐1‐butanol (AB). 2‐dimethylamino‐2‐methyl‐1‐propanol (DMAMP) is the only
N
‐substituted derivative of these compounds available in commercial quantities. The six commercial alkanolamines are highly soluble in water. They are generally very soluble in alcohols, slightly soluble in aromatic hydrocarbons, and nearly insoluble in aliphatic hydrocarbons. According to current DOT regulations, AMP, AMP‐95, DMAMP, DMAMP‐80, AEPD, and AB are all classified as combustible liquids. The commercial alkanolamines exhibit the chemical reactivity of both amines and alcohols, as other alkanolamines. Typically, they attack copper, brass, and aluminum, but not steel or iron. Alkanolamines are useful as amination agents. The reduction of nitro alcohols to alkanolamines is accomplished by hydrogenation in the presence of Raney nickel catalyst. Alkanolamines are only slightly toxic by ingestion. Undiluted DMAMP, AMP‐95, and AB cause eye burns and permanent damage if not washed out immediately. The 40% aqueous solution of TRIS AMINO is nonirritating to the eyes and skin. Alkanolamines are used in emulsions, pigment dispersion, resin solubilizers, catalysts, applications in oil and gas production, and in biomedical and synthetic applications.