Determination of the individual atomic site contribution to the electronic structure of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA).

We have studied the element and orbital-specific electronic structure of thin films of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) using a combination of synchrotron radiation-exited resonant x-ray emission spectroscopy, x-ray absorption spectroscopy, x-ray photoelectron spectroscopy, as well as density functional theory calculations. Resonant and non-resonant x-ray emission spectroscopies were used to measure the C and O 2p partial densities of state in PTCDA. Furthermore, resonant x-ray emission at the C and O K-edges is shown to be able to measure the partial densities of states associated with individual atomic sites. The flat molecular orientation of PTCDA on various substrates is explained in terms of the carbonyl O atom acting as a hydrogen-bond acceptor leading to multiple in-plane intermolecular C=O···H-C hydrogen bonding between carbonyl groups and the perylene core of the neighboring PTCDA molecules. We support this conclusion by comparison of our calculations to measurements of the electronic structure using element-, site-, and orbital-selective C and O K-edge resonant x-ray emission spectroscopy, and photoemission spectroscopy.

Using HapMap tools in pharmacogenomic discovery: the thiopurine methyltransferase polymorphism.

One purpose of the International HapMap Project is to provide a genome-wide resource to discover pharmacogenetic determinants of drug response. The thiopurine methyltransferase (TPMT) 719A>G single-nucleotide polymorphism (SNP) causes decreased TPMT activity, increased intracellular thiopurines, and drug toxicities. Using HapMap cell lines and 3.3 million SNPs, we tested whether the TPMT 719A>G SNP could be identified as predicting TPMT phenotype. Assuming TPMT was a candidate gene, five SNPs and four haplotypes predicted TPMT phenotype, two of which were in complete linkage disequilibrium with the functional 719A>G SNP. We also used a genome-wide approach to rank all 17,542 genes as predictors of TPMT activity. A TPMT haplotype, HAP1, significantly predicted TPMT phenotype; however, haplotypes of 96 genes ranked higher than TPMT. Our findings show that HapMap resources are useful for pharmacogenetic discovery when the candidate gene is known, but challenges remain for definitive gene identification when a genome-wide agnostic approach is employed.

Photophysics of PTCDA and Me-PTCDI thin films: effects of growth temperature.

The effect of deposition temperature on the photophysical properties of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N,N'-dimethylperylene-3,4,9,10-bis(dicarboximide) (Me-PTCDI) films is investigated with steady-state and time-resolved spectroscopy. Atomic force microscopy (AFM) images of the film surfaces show an increase in the dimensions of crystallites with substrate temperature, culminating in the formation of elongated crystallites on substrates held close to the sublimation temperature. In contrast, despite an improvement in the crystal quality, X-ray diffraction (XRD) studies indicate that the substrate temperature has a negligible effect on the molecular orientation; the PTCDA and Me-PTCDI molecules align parallel and tilted to the substrate surface, respectively. Both materials exhibit characteristic absorption, due to mixing between charge-transfer and Frenkel species, and broad structureless photoluminescence. Growth at elevated temperatures gives rise to increased low-energy absorption, attributed to the formation of charge-transfer species, and enhanced blue-shifted emission, although the effects are less pronounced for Me-PTCDI. Time-correlated single-photon counting data indicate that the enhancement coincides with a lengthening of the fluorescence decays, over the whole emission spectrum.

Epitaxial Templating of C60 with a Molecular Monolayer.

Commensurate epitaxial monolayers of truxenone on Cu (111) were employed to template the growth of monolayer and bilayer C60. Through the combination of STM imaging and LEED analysis we have demonstrated that C60 forms a commensurate 8 × 8 overlayer on truxenone/Cu (111). Bilayers of C60 retain the 8 × 8 periodicity of templated monolayers and although Kagome lattice arrangements are observed these are explained with combinations of 8 × 8 symmetry.

Two-dimensional core-shell donor-acceptor assemblies at metal-organic interfaces promoted by surface-mediated charge transfer.

Organic charge transfer (CT) complexes obtained by combining molecular electron donors and acceptors have attracted much interest due to their potential applications in organic opto-electronic devices. In order to work, these systems must have an electronic matching - the highest occupied molecular orbital (HOMO) of the donor must couple with the lowest unoccupied molecular orbital (LUMO) of the acceptor - and a structural matching, so as to allow direct intermolecular CT. Here it is shown that, when molecules are adsorbed on a metal surface, novel molecular organizations driven by surface-mediated CT can appear that have no counterpart in condensed phase non-covalent assemblies of donor and acceptor molecules. By means of scanning tunneling microscopy and spectroscopy it is demonstrated that the electronic and self-assembly properties of an electron acceptor molecule can change dramatically in the presence of an additional molecular species with marked electron donor character, leading to the formation of unprecedented core-shell assemblies. DFT and classical force-field simulations reveal that this is a consequence of charge transfer from the donor to the acceptor molecules mediated by the metallic substrate.

Charge recombination in CuPc/PTCDA thin films.

The recombination kinetics of photogenerated charge carriers in perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA) and copper phthalocyanine (CuPc) thin films grown by organic molecular beam deposition have been studied using transient absorption spectroscopy. Optical excitation is observed to generate long-lived polaron states, which exhibit power law recombination dynamics on time scales from microseconds to milliseconds. Studies as a function of excitation density and temperature, and comparison between heterostructures and PTCDA single layers, all indicate that this power law behavior results from trapping of PTCDA- polarons in localized states, with an estimated trap state density of approximately 6 x 10(17) polarons cm(-3). This recombination behavior is found to be remarkably similar to that previously observed for polymer/fullerene blends, suggesting that it may be generic to a range of semiconducting materials.

Syringe laws and pharmacy regulations are structural constraints on HIV prevention in the US.

OBJECTIVE: To review the legal and regulatory barriers that restrict pharmacy sales of syringes to injection drug users (IDUs) and to discuss how reducing these barriers can facilitate access to sterile syringes for IDUs and improve HIV prevention. BACKGROUND: IDUs' access to sterile syringes from community pharmacies in the United States is limited by state laws and regulations governing syringe sales. Restricted availability of sterile syringes from pharmacies is a structural barrier that greatly impedes HIV prevention for IDUs, who often share and reuse syringes because they cannot obtain and possess sterile syringes. These high-risk behaviors contribute to the transmission of HIV and other blood-borne pathogens among IDUs, their sexual partners, and their children. STATE EXPERIENCES: In Connecticut, because of high HIV prevalence among IDUs, restrictive syringe laws were changed. After the legal changes in Connecticut, both pharmacy sales of syringes in areas of high drug use and purchases of syringes in pharmacies (reported by IDUs) increased, while syringe sharing (reported by IDUs) decreased. Maine and Minnesota have made similar changes in laws. CONCLUSIONS: Increasing access to sterile syringes through pharmacies requires the repeal or modification of legal barriers. Pharmacy sale of syringes to IDUs is an inexpensive HIV prevention intervention with the potential to substantially reduce HIV transmission. Further studies are needed to document how changes to legal barriers can influence HIV prevention for IDUs.

A novel Escherichia coli lipoprotein expression vector.

A novel Escherichia coli (Ec) lipoprotein expression plasmid, pSJLP, was constructed. The plasmid contains a truncated alkaline phosphatase gene (phoA) located downstream from the Lac repressor gene lacIq and the IPTG inducible Ptac promoter. The phoA gene was truncated by deleting the native phoA signal sequence and fusing the truncated phoA gene to the lipoprotein signal sequence of the major Ec lipoprotein LPP. The recombinant LPP::PhoA fusion protein is produced and processed as a lipoprotein and can therefore be used as substrate for a novel signal peptidase II assay.

Inadequate bleach contact times during syringe cleaning among injection drug users.

Objectives were to measure syringe cleaning strategies used by injection drug users (IDUs) and to assess syringe contact with bleach during cleaning demonstrations. IDUs were interviewed about cleaning activities during their most recent injection episode; they demonstrated these activities on videotape. Coders reviewed the videotapes, categorized activities, and used stop watches to record bleach exposure. Of 161, 146 subjects reported cleaning at last injection, 85 (58%) of 146 used full strength bleach. Of bleach users, 20% had total contact time (duration of bleach inside syringe) of > or = 30 s; combining draw (time taken to fill syringe) and contact times, 54% of bleach users had total "flush" times of > or = 30 s. Median observed time per bleach flush was 16 s. Median reported cleaning times were twice as long as observed. Recent reports indicate 30 s of exposure to undiluted bleach is necessary to inactivate HIV in the laboratory; here, 80% of IDUs using bleach had contact of < 30 s. Judgment of contact time was inaccurate. On average, instructions advocating two bleach flushes may reach 30 s; here, half the subjects had insufficient time with two flushes. The majority showed inadequate techniques, therefore, alternate cleaning strategies should be developed.

Loss of maternal measles antibody during infancy in an African city.

Measles epidemics with 20% of the cases under nine months of age continue to occur in Brazzaville, Congo, even though measles vaccination coverage was 77% in the 12- to 23-month age group in 1986. In order to estimate the duration of passive immunity against measles, we conducted a serologic survey of infants aged 2 to 9 months. Measles antibody was measured from capillary blood with the plaque inhibition test. An antibody titre of 40 milli-International Reference Units per ml of serum (mIRU/ml) or less was defined as seronegative. Among the 252 infants studied, the proportion with detectable antibody dropped from 95.8% at 2 months of age to 48.5% at 4 months of age, and to 8.2% in the 7-8 month age group. A simple logistic model with age as the only variable provided an excellent fit to the observed values. Between the ages of 8 and 28 weeks, there was an almost steady decline of approximately 4.7% per week in the proportion of infants who were seropositive. These findings suggest that loss of maternal measles antibody during infancy might be faster than reported in other African populations. Giving measles vaccine to infants before the age of nine months currently recommended by the Expanded Programme on Immunization may be useful in some populations. Further studies of seroconversion and impact on measles are needed.

Fatal heat-related illness in naval cadets in Ecuador.

On 13 April 1982, after a 6 to 7 km training run on an extremely hot and humid day, 20 of 216 cadets at the Ecuadorian Naval Academy in Guayaquil became ill with symptoms of heat-related illness. Four of them suffered heat stroke, and three died. Illness was most highly associated with the amount of exercise performed that day but was significantly more common in first-year cadets than in older cadets. There were no differences in the anthropometric measurements of ill and well subjects. We conclude that heat-related illness can affect conditioned military personnel during routine training in severe weather and make recommendations for prevention.

Using seroprevalence data in managing public health programs.

An objective of the Centers for Disease Control (CDC) family of HIV seroprevalence surveys, conducted by State and local health departments, is the collection of seroprevalence data that may be useful in managing public health programs. In prevention programs, seroprevalence data may be used in allocating resources, in determining the types and amount of education, counseling, and testing services offered, and in identifying access points for HIV-infected persons for medical followup and care. Over time, data will be useful in detecting and following trends in HIV infection and in evaluating the impact of program activities to prevent HIV infection. No single seroprevalence survey is representative of the entire population of a metropolitan area. Each type of survey has strengths and limitations that must be considered when interpreting seroprevalence data. However, results from the family of surveys are the best available data because they are relatively unaffected by self-selection bias, they are standardized, and the information is collected over time. Characterization of the population surveyed and adherence to standard CDC protocols improve the quality of the data. Consultants in health departments and at CDC form a network for providing technical support and disseminating data to health care providers and program managers.

Where injecting drug users receive HIV counseling and testing.

In 1990, nearly 1.5 million human immunodeficiency virus (HIV) antibody tests were performed at publicly funded sites. Eight percent of those tests were performed for self-identified illegal injecting drug users (IDU). The authors examined data from 28 project areas using a client record data base that permitted an analysis of self-reported risk behavior by type of service delivery site. Among self-identified IDUs, 68 percent of those tested and 82 percent of those found to be seropositive had obtained HIV counseling and testing services in settings other than drug treatment centers. The findings indicate that HIV-prevention programs for IDUs need to be available in various service delivery settings, not just in drug treatment programs. Strong links and cooperation between sites offering HIV counseling and testing and sites providing drug treatment programs are important to preventing HIV transmission to and from IDUs.

HIV seroprevalence surveys in drug treatment centers.

Sharing of equipment used to inject illicit drugs intravenously is a risk factor for human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS). Systematic surveillance of HIV infection among intravenous drug users (IVDUs) in the United States is essential to monitor the HIV epidemic and to target and evaluate prevention programs for IVDUs and their partners. The most accessible segment of the largely covert population of IVDUs are those in drug treatment programs. In collaboration with State and local health departments and drug abuse treatment agencies, the Centers for Disease Control is conducting blinded (serologic test results not linked to identifiable persons) and nonblinded (in which clients voluntarily agree to participate) surveys of IVDUs entering drug treatment in 39 U.S. metropolitan areas. The same protocol is used in all participating drug treatment centers. Blinded surveys will be carried out annually to determine HIV seroprevalence rates in eligible IVDUs entering drug treatment and to monitor trends over time. Each year, nonblinded surveys of IVDUs entering drug treatment will assess self-reported drug use and sexual behaviors to help design educational interventions and to detect changes in behavior over time. This sentinel surveillance system, using a standardized methodology, will provide the best national and regional data available on the seroprevalence of HIV among IVDUs and the relationships of drug use, sexual behaviors, and HIV serologic status of IVDUs.

Minimizing process induced prooxidant stresses.

The adverse effects of trace metals, heat, steam and other conditions encountered in food processing relate to the acceleration of development of rancidity. Measures to retard oxidation of lipids, vitamins, pigments and proteins include elimination of prooxidants, removal of oxygen and use of blends of inhibitors formulated for specific substrates.

An investigation of medical examiner cases in which methadone was detected, Harris County, Texas, 1987-1992.

In 1991, media reports of an increase in the number of deaths attributed to methadone toxicity in Harris County, Texas, raised public concern about the safety of methadone. This concern was heightened by publicity surrounding the closure of three Harris County methadone maintenance treatment programs due to their poor compliance with federal methadone regulations. In response to this concern, the Texas Department of Public Health requested that the Centers for Disease Control and Prevention (CDC) assist in an epidemiologic study to determine the extent of methadone-related mortality in Harris County during 1991 and to determine the role of methadone maintenance treatment in these deaths. We reviewed cases investigated by the Harris County Medical Examiner's Office from 1987 through 1992 in which methadone was detected by postmortem drug testing. The autopsy reports for cases occurring in 1991 were also reviewed by three independent forensic pathologists who were asked to determine the role of methadone in the death. In addition, we attempted to document Harris County methadone maintenance treatment program enrollment for each decedent. We identified 91 decedents in whom methadone was detected at the time of death, with the largest number of cases occurring in 1991 (n = 27). Other substances, including alcohol, were detected in 85% of the cases. The Harris County Medical Examiner attributed 11 of the deaths to methadone toxicity. No more than three cases per year from 1987 through 1992 were attributed to methadone toxicity. In contrast, 34 deaths were attributed to polydrug toxicity, the largest number occurring in 1991 (n = 11). There was good agreement between the results of the independent review and the opinions of the Harris County Medical Examiner. Only 20% of the decedents were found to have been enrolled in a Harris County methadone maintenance treatment program at the time of death. Four people died of drug toxicity shortly after enrolling in a methadone maintenance treatment program. We found an increase in the number deaths occurring in Harris County, Texas, in 1991 in which methadone was detected. We also found that methadone blood levels were higher among decedents identified for 1991 and 1992 than among those identified in the previous years studied. However, we did not find evidence that the cause of these deaths could be attributed solely to methadone toxicity. Instead, for all years studied, the use of multiple drugs was the leading cause of death among people in whom methadone was detected. This finding points out the difficulties involved in determining the role of methadone as a cause of death.

Interpersonal distance, body orientation, and touch: effects of culture, gender, and age.

Video recordings of naturally occurring interactions in England, France, the Netherlands, Italy, Greece, Scotland, and Ireland were coded and analyzed to examine the effects of culture, gender, and age on interpersonal distance, body orientation, and touch. Results partially supported expected differences between contact cultures of southern Europe and noncontact cultures of northern Europe with respect to touch. More touch was observed among Italian and Greek dyads than among English, French, and Dutch dyads. In addition, an interaction effect between age and gender for body orientation suggested opposite development trends for mixed-sex dyads and male dyads. Whereas mixed dyads tended to maintain less direct orientations as they aged, male dyads maintained more direct orientations.

Comparison of axillary block techniques: is there a difference in success rates?

This study compared the success rates between two accepted methods of performing axillary blocks, the peripheral nerve stimulator (PNS) and the transarterial (TA) techniques. Success was based on blocking the nerves involved in the surgery. Following institutional review board approval and informed consent, 57 patients between the ages of 18 and 86 years of age scheduled for elective upper extremity surgery were studied. Patients were randomized and all blocks were performed according to the protocol for PNS and TA techniques using the dosage of local anesthetic based on patient weight. All patients were premedicated with fentanyl hydrochloride, 1 microgram/kg, and midazolam, 1 to 5 mg. Scoring was accomplished on a standardized form by one of two physicians, unaware of the technique, for 5 of the major nerves at 20 and 30 minutes after injection. Sensory blockade was determined by pinprick. Motor blockade was assessed according to a scale ranging from complete block to no effect. Two of the patients had vascular procedures, and the remainder were orthopedic procedures. There were no differences in the effectiveness on the musculocutaneous, radial, median, or ulnar nerves. There was a significant difference (P < 0.05) in the effectiveness at the axillary nerve. The transarterial technique was 66% effective as opposed to 47% for the PNS. There was no difference in the need for local supplementation or general anesthesia between the two groups. There were no significant side effects reported by the patients postoperatively. The axillary nerve was the only nerve with an increased success rate using the TA technique. This indicates that both techniques are equally acceptable.

Cultural and sex differences in touch avoidance.

250 male and female respondents from American, Mediterranean, Near Eastern, and Far Eastern cultures completed a self-report measure of touch-avoidance. Confirmatory factor analysis indicated factors for opposite-sex and same-sex touch-avoidance. These factors were used as dependent variables in a 4 x 2 (culture by sex) multivariate analysis of variance which yielded a significant interaction of culture by sex on opposite-sex touch-avoidance and a main effect of the respondents' sex on same-sex touch-avoidance.

Standard of care therapy for malignant glioma and its effect on tumor and stromal cells.

Glioblastoma is the most common and deadly of the primary central nervous system tumors. Recent advances in molecular characterization have subdivided these tumors into at least three main groups. In addition, these tumors are cellularly complex with multiple stromal cell types contributing to the biology of the tumor and treatment response. Because essentially all glioma patients are treated with radiation, various chemotherapies and steroids, the tumor that finally kills them has been modified by these treatments. Most of the investigation of the effects of therapy on these tumors has focused on the glioma cells per se. However, despite the importance of the stromal cells in these tumors, little has been done to understand the effects of treatment on stromal cells and their contribution to disease. Understanding how current standard therapy affects the biology of the tumor and the tumor stroma may provide insight into the mechanisms that are important to the inhibition of tumor growth as well as the biology of recurrent tumors.