UV photodecomposition of zinc acetate for the growth of ZnO nanowires

The thermal annealing of zinc precursors to form suitable seed layers for the growth of ZnO nanowires is common. However, the process is relatively long and involves high temperatures which limit substrate choice. In this study the use of a low temperature, ultra-violet (UV) exposure is demonstrated for photodecomposition of zinc acetate precursors to form suitable seed layers. Comparisons are made between ZnO nanowire growth performed on seed layers produced through thermal annealing and exposure to UV. The dependence of growth density and nanowire diameter on UV exposure time is investigated. Growth quality is confirmed with energy dispersive x-ray (EDX) and x-ray diffraction analyses. The chemical composition of the exposed layers is investigated with EDX and x-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) is utilized to investigate morphological changes with respect to UV exposure. The diameter and density of the resultant growth was found to be strongly dependent on the UV exposure time. UV exposure times of only 25-30 s led to maximum density of growth and minimum diameter, significantly faster than thermal annealing. EDX, XPS and AFM analyses of the seed layers confirmed decomposition of the zinc precursor and morphological changes which influenced the growth.

Flexographic printing-assisted fabrication of ZnO nanowire devices

In this study, the use of flexographic printing was investigated for low cost, high volume production of devices incorporating nanowires through the printing of zinc acetate precursors on a substrate used to form zinc oxide (ZnO) seeds for the growth of nanowires using a hydrothermal growth technique. The printing of precursors allows the selective area growth of ZnO nanowires, which has implications in high-yield production of devices incorporating ZnO nanowires. The work presented here achieved printed line widths of <60 μm with low edge distortion (<3 μm) using a printing plate with a line width of 50 μm. The hydrothermally grown ZnO nanowires show uniform density of growth over the printed area with nanowire diameters between 40 and 60 nm on both silicon and polyimide substrates. Energy-dispersive x-ray spectra showed contamination-free crystals with a 1:1 (zinc to oxygen) stoichiometry. Crystal orientation is along the c-axis with high quality crystalline structure shown using x-ray diffraction spectroscopy and high resolution transmission electron microscopy. A ZnO nanowire gas sensor, fabricated using the flexographic printing technique, is demonstrated. Such a printing-assisted fabrication offers low cost, high volume production of devices incorporating ZnO nanowires, ranging from gas sensors to field emission devices.

Inter-neonatal intensive care unit variation in discharge timing: influence of apnea and feeding management

BACKGROUND

Premature infants need to attain both medical stability and maturational milestones (specifically, independent thermoregulation, resolution of apnea of prematurity, and the ability to feed by mouth) before safe discharge to home. Current practice also requires premature infants to be observed in hospital before discharge for several days (margin of safety) after physiologic maturity is recognized.

OBJECTIVE

To compare postmenstrual age (PMA) at discharge in a homogeneous population of premature infants cared for in different neonatal intensive care units (NICUs) and to assess the impact on hospital stay of the recognition and recording of physiologic maturity and the required margin of safety.

METHODS

We studied premature infants delivered at 30 to 34 6/7 weeks gestational age (GA), free of significant medical or surgical complications. Medical records of 30 eligible infants consecutively discharged from the hospital before July 1997 from each of 15 NICUs in Massachusetts (9 level 2 and 6 level 3) were reviewed.

RESULTS

A total of 435 infants were included in the study sample. Mean (+/- standard deviation) GA and birth weight of the study population were 33.2 +/- 1.2 weeks and 2024 +/- 389 g, respectively. Infants were discharged at a similar PMA regardless of GA at birth. Considerable variation in the PMA at discharge between hospital sites was observed (range, 35.2 +/- 0.5 weeks to 36.5 +/- 1.2 weeks). Despite the homogeneous study population, hospitals in which infants had the latest PMA at discharge also recorded mature cardiorespiratory and feeding behavior at an older age. Longer duration of pulse oximetry use was associated with later resolution of apnea. Differences in the duration of the margin of safety between sites did not contribute to variation in hospital stay.

CONCLUSION

NICUs vary widely in length of hospital stay for healthy premature infants. We speculate that this variation results in part from differences in monitoring for and documentation of apnea of prematurity and feeding behavior.

A model to assess the infection potential of jet injectors used in mass immunisation

Jet injectors are needleless injectors that penetrate skin with high-pressure fluid. They have potential advantages over needles and syringes in mass immunisation programs, but concerns over their capacity to transfer blood-borne viruses have been a barrier to acceptance. Hepatitis B infection can transmit in 10 pl of blood; detection of such low volumes presents severe difficulties to such assessments. A model to assess jet injector safety was developed using injection of an inert buffer into calves and assaying the next injector discharge, representing the next dose of vaccine, for blood using a highly sensitive ELISA. Four injectors were tested: two with reusable heads and direct skin contact, one with single-use injector heads and one where the injector head discharged at a distance from the skin. All injectors tested transmitted significant (over 10 pl) volumes of blood; the volumes and frequency of contamination varied with injector. The source of the contamination was consistent with contamination by efflux of injected fluid and blood from the pressurised pocket in tissue that is formed during injection. This insight should inform the design of safe jet injectors.

Specific detection of DNA and RNA targets using a novel isothermal nucleic acid amplification assay based on the formation of a three-way junction structure

The formation of DNA three-way junction (3WJ) structures has been utilised to develop a novel isothermal nucleic acid amplification assay (SMART) for the detection of specific DNA or RNA targets. The assay consists of two oligonucleotide probes that hybridise to a specific target sequence and, only then, to each other forming a 3WJ structure. One probe (template for the RNA signal) contains a non-functional single-stranded T7 RNA polymerase promoter sequence. This promoter sequence is made double-stranded (hence functional) by DNA polymerase, allowing T7 RNA polymerase to generate a target-dependent RNA signal which is measured by an enzyme-linked oligosorbent assay (ELOSA). The sequence of the RNA signal is always the same, regardless of the original target sequence. The SMART assay was successfully tested in model systems with several single-stranded synthetic targets, both DNA and RNA. The assay could also detect specific target sequences in both genomic DNA and total RNA from Escherichia coli. It was also possible to generate signal from E.coli samples without prior extraction of nucleic acid, showing that for some targets, sample purification may not be required. The assay is simple to perform and easily adaptable to different targets.

Heterologous expression of soluble methane monooxygenase genes in methanotrophs containing only particulate methane monooxygenase

The methanotrophs Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b contain particulate methane monooxygenase (pMMO) and soluble methane monooxygenase (sMMO) genes. Other methanotrophs such as Methylomicrobium album BG8 and Methylocystis parvus OBBP contain only pMMO genes. Although molecular genetic techniques are poorly developed in methanotrophs, sMMO genes were expressed in methanotrophs normally containing only pMMO genes. This was achieved by conjugation using broad-host-range plasmids containing the native promoter and sMMO genes from Mc. capsulatus (Bath) and Ms. trichosporium OB3b. sMMO genes derived from Ms. trichosporium OB3b were expressed in an active form in Mcy. parvus OBBP and in Mm. album BG8. Therefore, all of the genes required for active sMMO synthesis were contained on the broad-host-range plasmids and were expressed in the heterologous hosts. Constitutive synthesis of pMMO was observed in Mm. album BG8 when grown at high and low copper-to-biomass ratios, while transcription of the recombinant sMMO genes was only observed under growth conditions of low copper-to-biomass ratios. Therefore, the regulatory protein(s) for sMMO synthesis was also present on the plasmid used, or the heterologous host contained a regulatory system for sMMO. Expression of sMMO genes in methanotrophs containing only pMMO will assist further investigations on the expression and regulation of MMO genes in methanotrophs.

Heterologous expression of alkene monooxygenase from Rhodococcus rhodochrous B-276

Alkene monooxygenase (AMO) from Rhodococcus rhodochrous (formerly Nocardia corallina) B-276 is a three-component enzyme system encoded by the four-gene operon amoABCD. AMO catalyses the stereoselective epoxygenation of aliphatic alkenes, yielding primarily R enantiomers. The presumed site of alkene oxygenation is a dinuclear iron centre similar to that in the soluble methane monooxygenases of methanotrophic bacteria, to which AMO exhibits a significant degree of amino acid sequence identity. The AMO complex was not expressed in Escherichia coli, at least partly because that host did not produce all of the AMO polypeptides. Expression of AMO was achieved in Streptomyces lividans by cloning the AMO genes into the thiostrepton-inducible expression plasmid pIJ6021. No background of AMO activity was detected in S. lividans cells without amoABCD and expression of AMO activity, at a level comparable to that from wild-type R. rhodochrous B-276, coincided with appearance of the AMO subunits. Recombinant AMO activity in cell-free extracts of S. lividans was stimulated by the addition of NADH and produced R-epoxypropane with comparable enantiomeric excess to AMO purified from the original organism. Although the whole AMO complex could not be expressed in E. coli, the functional coupling protein (AmoB) and reductase (AmoD) were expressed individually in E. coli as fusions with glutathione S-transferase. The expression systems described here now allow structure/function studies on AMO to be carried out by site-directed mutagenesis.

Auto-disable syringes for immunization: issues in technology transfer

WHO and its partners recommend the use of auto-disable syringes, "bundled" with the supply of vaccines when donor dollars are used, in all mass immunization campaigns, and also strongly advocate their use in routine immunization programmes. Because of the relatively high price of auto-disable syringes, WHO's Technical Network for Logistics in Health recommends that activities be initiated to encourage the transfer of production technology for these syringes as a means of promoting their use and enhancing access to the technology. The present article examines factors influencing technology transfer, including feasibility, corporate interest, cost, quality assurance, intellectual property considerations, and probable time frames for implementation. Technology transfer activities are likely to be complex and difficult, and may not result in lower prices for syringes. Guidelines are offered on technology transfer initiatives for auto-disable syringes to ensure the quality of the product, the reliability of the supply, and the feasibility of the technology transfer activity itself.

Inactivation of the regulatory protein B of soluble methane monooxygenase from Methylococcus capsulatus (Bath) by proteolysis can be overcome by a Gly to Gln modification

The regulatory protein B of soluble methane monooxygenase (sMMO) from Methylococcus capsulatus (Bath), exists as a mixture of the full-length active form and truncated forms, B' and B". Electrospray ionisation mass spectrometry (ESI-MS) was used to identify a cleavage site between Met12 and Gly13, such that 12 amino acids were lost from the N-terminus of protein B. This truncate was designated B' and molecular masses were assigned to proteins B and B' of 15,852.6+/-0.4 Da and 14,629.5+/-0.3 Da, respectively. A cleavage site between Gln29 and Val30 was also identified such that 29 amino acids were lost from the N-terminus of protein B. This truncate was designated B" and had a molecular mass of 12,709.93+/-0.02 Da. Proteins B' and B" were found to be inactive in the sMMO system. Addition of protease inhibitors or the heterologous expression of protein B in various strains of lon-deficient or ompT-deficient Escherichia coli, did not inhibit B' formation. Expression of protein B as a glutathione S-transferase fusion protein and subsequent purification of protein B from E. coli using affinity chromatography resulted in preparations of protein B with higher enzyme activities than that of wild-type protein B. However, ESI-MS confirmed that protein B' was still present. Alteration of the Met12-Gly13 cleavage site to Met12-Gln13 revealed that the stability of G13Q at 20 degrees C and 37 degrees C was higher than that of wild-type preparations. ESI-MS indicated that protein B' was absent and could only be identified after prolonged incubation at room temperature. The amount of active protein B present in the cell may be controlled by protein B cleavage, thereby regulating electron transfer. Alternatively, it may allow protein B to maintain a certain conformation necessary for enzyme activity and this may control the activity of sMMO in response to the supply of methane to the cell.

Bringing reality to the job hunt process. Interview by Barbara J. Linney

A substantial percentage of the positions that open in medical management are filled through the use of recruitment firms. This is especially true of more senior positions, but it applies across the full spectrum of openings. If the working arrangement between the recruitment firm and the potential candidate is to be effective, certain key ingredients are necessary. The author interviewed a selection of principals of recruitment firms that operate extensively or exclusively in the medical management sector of executive recruitment. What she discovered about their "wish lists" for candidates' characteristics and levels of job hunting sophistication are summarized in the following statements.

Developmental transitions in the myosin heavy chain phenotype of human respiratory muscle

We studied the expression of myosin heavy chain (MHC) isoforms in the costal diaphragm (DIA) and the genioglossus (GG) muscles from 16 to 42 weeks gestation in the human using Western blotting techniques. Embryonic/neonatal MHC (MHCemb/neo) was the predominant isoform expressed in the DIA and GG at 16-24 weeks gestation. Subsequently, MHCemb/neo expression declined and the expression of MHCslow and MHC2A increased. At term, the DIA MHC phenotype was a composite of MHCemb/neo (15% of the total MHC complement), MHCslow (32%), MHC2A (47%), and MHC2B (6%); whereas, the GG was largely comprised of MHC2A (74%). We conclude that human DIA and GG demonstrate temporally dependent changes in MHC expression during gestation- and muscle-specific MHC phenotypes as they approach term.

The physician executive "arrives"--a new generation prepares for the future

The recent rise in the number of physician executives in the health care industry vividly demonstrates that a genuinely new generation of physician executives is seeking to combine the sensitivity of their clinical skills with the business acumen that today's health care organizations need to prosper and grow. But physicians who are preparing themselves to be selected one day as chief executive officers by hospitals, integrated systems, and managed care organizations should understand that the CEO role is radically different from that of the CEO of a physician practice. The corporate CEO role requires the management of managers and responsiveness to the organization's board. Those who imagine that the corporate CEO role bears any resemblance to the autonomous, independent existence of the practitioner are certain to have a rough time.

What kind of leaders will be successful?

The U.S. health care system is fundamentally changing. The pace of change is swift but will vary, depending on regional market forces and state legislative mandates. This complex change is leading to rapid market consolidation of providers and insurers into organizations called "integrated health care systems." There is, as yet, no proven role model that will guarantee success. The purpose of this article is two-fold: To help individuals who see an expanding role for themselves in integrated health care management decide if they have what it is going to take to be successful. To identify individual management training needs by use of a self-evaluation tool. Some of the needed skills can be enhanced by education and experience. However, some are personality and style characteristics that may not be changeable.

Panel sees high demand for diverse CFO skills

A more sophisticated healthcare industry, challenged by competition and payer demands, also looks for sophistication when filling its senior financial positions. Individuals with experience in managed care contract negotiations, knowledge of hospital-physician ventures, and superior planning and treasury management skills are increasingly sought by hospitals. Some organizations also may single out chief financial officers able to assume broader administrative duties, including chief executive officer positions. These are among the observations of a panel convened by HFMA to discuss recent trends in healthcare executive recruiting. Highlights of the session, moderated by HFMA President Richard L. Clarke, FHFMA, follow.

Physician executives in the '90s: report of a national survey

In fall 1990, Witt Associates again catalogued the progress of physicians as they obtain management positions of increasing importance. The firm has conducted a continuing study of the position since 1979. The current survey of vice presidents of medical affairs/medical directors renders a candid portrait of the physician manager. The profile that emerges is a 53-year-old white male, working almost 50 hours a week in a full-time position, appointed by the hospital and reporting to the Chief Executive Officer. This individual is board certified and has major responsibilities for quality assurance, credentialing, risk management, and utilization review. His or her salary is into six figures.

Medical directors: fewer in number, yet stronger in clout

In June 1983, fewer hospitals employed medical directors than in 1981, yet the medical director position seems to be gaining in importance and prestige as hospitals face continuing challenges.

Stability of further-attenuated measles vaccines

Accelerated stability tests on lyophilized measles vaccines show two distinct mechanisms of virus inactivation. A rapid initial loss of infectivity occurs only on exposure to temperatures above the ambient temperature. This loss is temperature related and may be attributable to the movement of residual moisture from the virus pellet into the void space of the vial. Subsequent inactivation of virus occurs at all temperatures as a first-order reaction that follows Arrhenius kinetics. Integration of values for these two components allows precise prediction of vaccine stability at any temperature. Analysis of the results obtained for greater than 30 vaccines shows that those which are stable for one week at 37 C have a predicted life of more than one year at 8 C. This simple test is now being applied to the identification of unstable products. The rate of this reaction is closely, if conservatively, matched by a time-temperature color indicator, which may be useful for monitoring vaccine quality.

Pulsatile secretion of luteinizing hormone in children

The gonadotropin secretory patterns of 22 sexually immature children were analyzed in detail to determine whether pulsatile secretion occurs before the onset of puberty. Eight endocrinologically normal children, 13 children with isolated GH deficiency, and 1 girl with 45X gonadal dysgenesis were divided into 2 groups according to bone age. Group A children had bone ages less than 10 yr, and group B had bone ages between 10-11.5 yr. Blood samples were drawn every 20 min for periods of 3-11 h during both the day and night; in addition, 12-h urine collections were made for gonadotropin determinations. Mean nocturnal concentrations of LH and FSH were significantly greater than daytime values in 8 of 15 and 5 of 15 children in group A and in 6 of 7 and 1 of 7 in group B, respectively. Nocturnal urinary excretion of LH and FSH was significantly greater in group A children. Eight children in group A, including 4 whose bone ages were less than 5 yr, and 4 group B children had discernible LH pulses. LH pulses were detected during the day and night in both groups. LH pulse amplitude was greater during the night in both groups, but was greatest in group B (A, 1.9 +/- 0.2 mIU/ml; B, 3.0 +/- 0.3 mIU/ml). In children who demonstrated pulsatile secretion, LH pulse frequency appeared to be similar during the day and night and was slightly faster in the older children (A, every 3 h; B, every 2 h). These studies demonstrated that LH is secreted in a pulsatile manner well before the onset of puberty. Furthermore, the gonadotropin secretory pattern characteristic of early puberty results from the amplification of an already existing circadian pattern of gonadotropin secretion.

Hiring a medical director

Hiring a medical director involves more than specifying the basic qualifications a candidate should have. The hospital board and administration should clearly delineate its policy toward practice privileges for the medical director and the reporting relationship desired. This article also examines how to begin a search, how to tailor a campaign to attract qualified candidates, and various compensation considerations.

Competence in medicine

During the past decade, medical educators have spent time discussing and attempting to define medical competence. There appears to be some confusion as to why definitions of competence are important and how one might describe in a logical fashion the elements of competence for physicians. Here, we try to clarify what is meant by competence, to describe how definitions of competence are of value to students, educators, institutions and the public, and to provide a conceptualization of the elements of a definition of competence in medicine.

Does our hospital need a medical administrator?

Many hospitals today are considering creating the position of full-time paid medical administrator to facilitate medical staff involvement in the corporate process and meet increasing medico-administrative demands. But establishing such a position is not necessarily the best course for all hospitals to follow. This article details some of the consideration involved in assessing the need for a medical director and possible repercussions of the decision.

A profile of today's medical director

A profile of the medical director position established at a growing number of hospitals, and those who serve in that position, was obtained through a nationally distributed questionnaire. Also determined were the types of hospitals that have made, or are likely to make, this new position a part of their organization.

A study of the practice of otorhinolaryngology in the United States. Initial findings

Results of a national survey of nonfederal otorhinolaryngologist regarding their practices provide the following portrait of the typical physician who specializes in otorhinolaryngology: male, between 35 and 45 years old, engaged in solo practice in a metropolitan area in the southern part of the country. He works a 46-hour week, devoting most of his time to patient care. During a typical week, he sees 113 patients, mostly outside the hospital. Half of his patients are male; although their average age is 35, one fourth of his patients are under 15 years. Every third patient is new to him; every other patient has been referred. He spends almost 15 minutes with each patient, many of whom he is seeing on a continuous basis for a problem involving the ear. He prescribes medications in roughly half of all encounters; every tenth patient requires surgery. He rates the majority of the problems he encounters as chronic, and of minor to moderate severity and urgency--for which he provides services of limited complexity or less. He seldom refers his patients.

Effectiveness of continuing medical education: a review of the evidence

Evidence regarding the effectiveness of continuing medical education (CME) is reviewed in terms of three possible end- products : physician competence, physician performance, and patient health status. Results of this review are presented in the context of recent increases in mandatory CME policies and the corresponding cost of such policies to the nation. The number of CME activities is evidently on the increase. Yet, according to conventional wisdom, CME is not effective. To the contrary, about half of the 47 evaluation studies published since 1960 reported demonstrable improvement in at least one of the three end-products following CME. However, methodological shortcomings in many of these studies make it impossible to conclude that the improvements were caused by the CME. The authors discuss the need for more research surrounding the subject of CME and its effectiveness.

A study of the practice of dermatology in the United States. Initial findings

A nationwide study of the practice activities of dermatologists reports that dermatology is a predominantly outpatient specialty, with 97% of patient encounter occurring outside of the hospital. The average dermatologist cares for approximately 7,000 patients a year and functions almost exclusively as a specialist, with only 2.2% of his cases related to nondermatologic problems. The dermatologist performs a type of primary care, however, with seven out of ten patients being self-referred. Eighty-seven percent of dermatologic encounters can be categorized into 25 disease conditions. This study serves to increase the understanding of how the dermatologist cares for his patients.

A national study of medical and surgical specialties. II. Description of the survey instrument

The survey instrument used in the national study of physician activities conducted by the University of Southern California, Division of Research in Medical Education, is a log-diary in which physicians kept a record of their actual professional activities. The log-diary focused on use of physician time and patient encounters and employed numerical coding of activities and patient encounters in a highly structured format. Compared with instruments used in similar studies, this log-diary appears to gather a greater breadth and depth of information about physician practice patterns.

A cold box for the transport and storage of vaccines

A cold box capable of maintaining a temperature below +4 degrees C for 1 week was constructed and tested in the laboratory and under field conditions. Cooling is produced by commercial cold packs precooled in a deep-freeze or the freezing compartment of a refrigerator. The box can take approximately 3000 doses of vaccine and is simple, cheap and strong. It is primarily intended for storage of vaccines during field trips by vaccination teams, as an alternative to the refrigerator in regional and peripheral stores in the case of an electrical power failure, and for the delivery of vaccines from regional store to the district.