Electronic Enhancement of the Exciton Coherence Time in Charged Quantum Dots.

Minimizing decoherence due to coupling of a quantum system to its fluctuating environment is at the forefront of quantum information and photonics research. Nature sets the ultimate limit, however, given by the strength of the system's coupling to the electromagnetic field. Here, we establish the ability to electronically control this coupling and enhance the optical coherence time of the charged exciton transition in quantum dots embedded in a photonic waveguide. By manipulating the electronic wave functions through an applied lateral electric field, we increase the coherence time from ∼1.4 to ∼2.7 ns. Numerical calculations reveal that longer coherence arises from the separation of charge carriers by up to ∼6 nm, which leads to a 30% weaker transition dipole moment. The ability to electronically control the coherence time opens new avenues for quantum communication and novel coupling schemes between distant qubits.

Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy.

We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 µm FWHM x-ray spot size, containing ∼10(6) photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >10(7) laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.

Monolithic device for modelocking and stabilization of frequency combs.

We demonstrate a device that integrates a III-V semiconductor saturable absorber mirror with a graphene electro-optic modulator, which provides a monolithic solution to modelocking and noise suppression in a frequency comb. The device offers a pure loss modulation bandwidth exceeding 5 MHz and only requires a low voltage driver. This hybrid device provides not only compactness and simplicity in laser cavity design, but also small insertion loss, compared to the previous metallic-mirror-based modulators. We believe this work paves the way to portable and fieldable phase-coherent frequency combs.

Photon antibunching from a single lithographically defined InGaAs/GaAs quantum dot.

We demonstrate photon antibunching from a single lithographically defined quantum dot fabricated by electron beam lithography, wet chemical etching, and overgrowth of the barrier layers by metalorganic chemical vapor deposition. Measurement of the second-order autocorrelation function indicates g(2)(0)=0.395±0.030, below the 0.5 limit necessary for classification as a single photon source.

Expression and sequence analysis of candidates for the 1p36.31 tumor suppressor gene deleted in neuroblastomas.

Neuroblastomas are characterized by 1p deletions, suggesting that a tumor suppressor gene (TSG) resides in this region. We have mapped the smallest region of deletion (SRD) to a 2 Mb region of 1p36.31 using microsatellite and single nucleotide polymorphisms. We have identified 23 genes in this region, and we have analysed these genes for mutations and RNA expression patterns to identify candidate TSGs. We sequenced the coding exons of these genes in 30 neuroblastoma cell lines. Although rare mutations were found in 10 of the 23 genes, none showed a pattern of genetic change consistent with homozygous inactivation. We examined the expression of these 23 genes in 20 neuroblastoma cell lines, and most showed readily detectable expression, and no correlation with 1p deletion. However, 7 genes showed uniformly low expression in the lines, and 2 genes (CHD5, RNF207) had virtually absent expression, consistent with the expected pattern for a TSG. Our mutation and expression analysis in neuroblastoma cell lines, combined with expression analysis in normal tissues, putative function and prior implication in neuroblastoma pathogenesis, suggests that the most promising TSG deleted from the 1p36 SRD is CHD5, but TNFRSF25, CAMTA1 and AJAP1 are also viable candidates.

Adolescent children of drug-abusing parents.

The effects of a substance-abusing parent on a child are wide-spread, and unfortunately they follow that child well into adolescence and adulthood. Cognitive difficulty, poor judgment, and conduct problems are but a few of the sequelae, and similar results are seen whether the drug is alcohol or cocaine or another illicit substance. In addition to affecting the biology of the adolescent from the perinatal period, parental substance abuse often causes a disrupted, chaotic home, financial insecurity, and exposure of the teen to illegal substances and violence. The emotional toll on the adolescent is steep, and the overall cost to the health care system is enormous. Ultimately, many of these adolescents progress to substance abuse themselves. Health care providers need to be sensitive to the possibility of substance abuse in the home, and should aggressively pursue early treatment/therapy options for those teens at risk.

Voucher-based reinforcement of opiate plus cocaine abstinence in treatment-resistant methadone patients: effects of reinforcer magnitude.

The study tested a voucher-based abstinence reinforcement procedure for reducing opiate and cocaine use in a population of treatment-resistant opiate- and cocaine-abusing methadone patients. Vouchers exchangeable for goods and services were contingent on abstinence from both opiates and cocaine. In two conditions, participants could earn up to $374 or $3,369 in vouchers for providing opiate- and cocaine-free urine samples. Participants received a daily 60-mg dose of methadone. The dose was increased in a second phase, and the voucher conditions were replicated. Analyses of both phases revealed trends toward greater abstinence under the high voucher condition and suggested that higher doses may enhance the efficacy of voucher reinforcement. The results show that reinforcement for abstinence from 2 drugs simultaneously can be effective even in a treatment-resistant population.

A reinforcement-based therapeutic workplace for the treatment of drug abuse: six-month abstinence outcomes.

This study evaluated a novel drug abuse treatment, the Therapeutic Workplace. In this treatment, patients are paid to perform jobs or to participate in job training. Salary is linked to abstinence by requiring patients to provide drug-free urine samples to gain access to the workplace. Pregnant and postpartum drug abuse patients (N = 40) were randomly assigned to a Therapeutic Workplace or usual care control group. Therapeutic Workplace participants were invited to work 3 hr every weekday for 6 months and could earn up to $4,030 in vouchers for abstinence, workplace attendance, and performance. On average, 45% of participants attended the workplace per day. Relative to controls, the Therapeutic Workplace nearly doubled patients' abstinence from opiates and cocaine (33% vs. 59% of thrice-weekly urine samples drug negative, respectively, p < .05). The Therapeutic Workplace can effectively treat heroin and cocaine abuse in pregnant and postpartum women.

The complestatins as HIV-1 integrase inhibitors. Efficient isolation, structure elucidation, and inhibitory activities of isocomplestatin, chloropeptin I, new complestatins, A and B, and acid-hydrolysis products of chloropeptin I.

From the screening of a microbial extract library, isocomplestatin (1), a new axial-chiral isomer of complestatin (2) which is a known rigid bicyclic hexapeptide, was identified as a potent natural product inhibitor of HIV-1 integrase, a unique enzyme responsible for viral replication. Isocomplestatin showed inhibitory activities (IC(50)) in coupled 3'-end processing/strand transfer (200 nM), strand transfer (4 microM), and HIV-1 replication (200 nM) in virus-infected cells. Attempted large-scale isolation of 1 by the literature method, used for the isolation of complestatin, led to lower yield and limited availability. We have developed several new, two-step, high-yielding absorption/elution methods of isolation based on reverse-phase chromatography at pH 8 that are applicable to scales from one gram to potential industrial quantities. We have also discovered and determined the structure of two new congeners of 1, namely, complestatins A (4) and B (5), with almost equal HIV-1 integrase activity. They differ from 1 at C2' and C3' of the tryptophan moiety (residue F). Selective acid hydrolysis of chloropeptin I (3), itself a known acid-catalyzed rearranged isomer of 1 and 2 (8'- vs 7'-substitution in tryptophan residue F, respectively), an isomer of complestatin, and isocomplestatin resulted in a number of fragments (6-10) with retention of most of the HIV-1 integrase activity. The structure-activity relationship as revealed by these compounds could possibly lead to the design of better inhibitors or understanding of the HIV-1 integrase target.

Effects of urine testing frequency on outcome in a methadone take-home contingency program.

We examined the effects of urine testing frequency on treatment outcome in a contingent methadone take-home program. Study patients who submitted<80% opiate and/or cocaine positive urines during a 5-week baseline received 60 mg methadone throughout the study, submitted urine samples on Monday, Wednesday, and Friday, and were randomized into one of three take-home incentive conditions. Study patients could receive three take-home doses per week if one urine sample randomly selected each week (Weekly; n=16) or each month (Monthly; n=18) was negative for opiates and cocaine. Take-homes for Random Drawing control patients (n=19) were determined weekly independent of urine test results. Subjects in the Weekly group showed an immediate increase from baseline in percentage of drug-free urines; those in the Monthly group showed a gradual increase over the first 3 months; and those in Random Drawings showed a decline in percentage of drug-free urines over time. The percentage of patients with sustained (8 or more weeks) opiate and cocaine abstinence was 56.6, 38.9 and 10.5% for Weekly, Monthly and Random Drawing groups, respectively (P<0.002). These results confirm that methadone take-homes contingent on drug-free urines prevent a decline in treatment performance over time and suggest that abstinence can be sustained with urine testing conducted as infrequently as once a month.

The effectiveness of incentives in enhancing treatment attendance and drug abstinence in methadone-maintained pregnant women.

This study examined the effectiveness of short-term contingency management for eliminating cocaine use and increasing full day treatment attendance with pregnant methadone-maintained women randomly assigned to either an escalating voucher incentive schedule (n=44) or non-incentive (n=36) conditions. Full day treatment attendance and urine toxicology for cocaine and heroin were assessed and consequated for 14 days. The escalating voucher incentive schedule significantly increased full day treatment attendance and drug abstinence compared to the non-incentive schedule. These results suggest that reinforcing the co-occurrence of two required behaviors (treatment attendance and abstinence from illicit drug use) is effective, and may be an important adjunct to methadone pharmacotherapy for treating pregnant drug dependent women.

Non-classic 21-hydroxylase deficiency in an 18-year-old female athlete. A case report

Background: In non-classic 21-hydroxylase deficiency, age at presentation and genital findings are variable. Late diagnosis with dramatic signs of virilization precludes early treatment and thus prevention of anatomic and psychosocial consequences. The following case illustrates the complexity of late diagnosis.Case: An 18-year-old West Indian female was seen for evaluation of clitoromegaly and hirsutism discovered in the emergency department when she presented after sexual assault. She had allegedly been drugged and raped in her dorm room. She was a college student with an athletic scholarship and had a striking masculinized, broad-shouldered appearance. She denied any use of anabolic steroids or other drugs. Menarche was at age 16 with infrequent menses. She was sexually active with 4 life-time partners, all male. On physical exam, her height was 152 cm, weight 50 kg, blood pressure 110/70 mm Hg. Breasts were hypoplastic with hyperpigmented nipples. She was hirsute with a Ferriman-Gallwey score of 14. Genitalia were abnormal with clitoris measuring 5.5 x 1.5 cm and posterior labial fusion. Initial non-fasting serum 17-hydroxyprogesterone level was 2890 ng/dL, testosterone was 274 ng/dL, and cortisol was 9 &mgr;g/dL. Chromosome analysis was 46, XX and ACTH stimulation test confirmed the diagnosis of 21-hydroxylase deficiency. The patient was initially reluctant to begin glucocorticoid treatment because of concern that it would decrease her muscle mass and negatively impact on her athletic performance and scholarship support. One year after diagnosis and 10 months after beginning treatment, she elected surgical correction of her clitoromegaly because of extreme embarrassment over having erections during sex. She underwent excision of most of the corpus cavernosum with repositioning of the glans. The neurovascular elements were preserved. The patient is pleased with the cosmetic result and reports no change in achieving orgasm. She has not notices any change in muscle mass or athletic performance since beginning glucocorticoid therapy.Conclusion: This case illustrates the somatic and genital abnormalities as well as the psychosocial impact of a delayed diagnosis of 21-hydroxylase deficiency in this young female athlete.

Effects of a short-term health promotion intervention for a predominantly African-American group of stroke survivors.

BACKGROUND: The study examined the effects of a 12-week health promotion intervention for a predominantly urban African-American population of stroke survivors. DESIGN: A pre-test/post-test lag control group design was employed. PARTICIPANTS/SETTING: Participants were 35 stroke survivors (9 male, 26 female) recruited from local area hospitals and clinics. MAIN OUTCOME MEASURES: Biomedical, fitness, nutritional, and psychosocial measures were employed to assess program outcomes. RESULTS: Treatment group made significant gains over lag controls in the following areas: (1) reduced total cholesterol, (2) reduced weight, (3) increased cardiovascular fitness, (4) increased strength, (5) increased flexibility, (6) increased life satisfaction and ability to manage self-care needs, and (7) decreased social isolation. CONCLUSION: A short-term health promotion intervention for predominantly African-American stroke survivors was effective in improving several physiological and psychological health outcomes.

Efficient syntheses, human and yeast farnesyl-protein transferase inhibitory activities of chaetomellic acids and analogues.

Chaetomellic acids are a class of alkyl dicarboxylic acids that were isolated from Chaetomella acutiseta. They are potent and highly specific farnesyl-pyrophosphate (FPP) mimic inhibitors of Ras farnesyl-protein transferase. We have previously described the first biogenetic type aldol condensation-based total synthesis of chaetomellic acid A. Modification of the later steps of that synthesis resulted in the efficient syntheses of chaetomellic acids A and B in three steps with 75-80% overall yield. In this report, details of the original total syntheses of chaetomellic acids A, B and C, the new syntheses of acids A and B and structure-activity relationship of these compounds against various prenyl transferases including human and yeast FPTase and bovine and yeast GGPTase I are described. Chaetomellic acids are differentially active against human and yeast FPTase. Chaetomellic acid A inhibited human and yeast FPTase activity with IC50 values of 55 nM and 225 microM, respectively. In contrast, chaetomellic acid C showed only a 10-fold differential in inhibitory activities against human versus yeast enzymes. In keeping with molecular modeling-based predictions, the compounds with shorter alkyl side chains (C-8) were completely inactive against FPTase.

The brief abstinence test: voucher-based reinforcement of cocaine abstinence.

This study assessed the effectiveness of a brief abstinence reinforcement procedure for initiating cocaine abstinence in methadone maintenance patients. On Monday of the test week, 72 cocaine-abusing methadone patients were offered a $100 voucher if urine samples collected on Wednesday indicated that they had abstained from cocaine across that 2-day period. A patient was considered abstinent and the voucher delivered if the urine benzoylecgonine concentration decreased by 50% from Monday to Wednesday (quantitative criterion) or if the concentration of Wednesday's urine sample was < or = 300 ng/ml. Overall, 79% of study patients showed urinalysis evidence of abstention from cocaine between Monday and Wednesday of the test week. In a subsample with complete data (n = 50), significantly more patients abstained from cocaine from Monday to Wednesday of the test week (84%) than from Monday to Wednesday of the week before (36%) or after (32%) the test week. Furthermore, while almost all patients (94%) decreased their benzoylecgonine concentration from Monday to Wednesday of the test week, significantly fewer patients' benzoylecgonine concentrations decreased from Monday to Wednesday of the week before (56%) or after (48%) the test week. This highly efficacious procedure may have clinical application where reliable abstinence initiation is desired, either on a temporary basis (e.g. sobriety sampling) or at the start of longer-term interventions. It may also be possible to use the brief abstinence test as an experimental model to assess the effects of other therapeutic interventions on abstinence initiation in treatment settings.

Inhibitors of farnesylation of Ras from a microbial natural products screening program.

Mutant ras oncogenes are associated with various human tumors such as pancreas, colon, lung, thyroid, bladder and several types of leukemia. Prenylation of Ras proteins plays a major role in cell proliferation of both normal and cancerous cells. Normal and oncogenic Ras proteins are posttranslationally modified by a farnesyl group that promotes membrane binding. Inhibitors of farnesyl protein transferase (FPTase), the enzyme that catalyzes the prenylation of Ras proteins, inhibit growth of tumor cells. In an effort to identify structurally diverse and unique inhibitors of FPTase, a program devoted to screening of natural products was initiated. This effort led to the identification of 10 different families of compounds, all of which selectively inhibit FPTase with a variety of mechanisms that are reviewed in this manuscript. These compounds originated from the fermentations of a number of microorganisms, either actinomycetes or fungi, isolated from different substrates collected in tropical and temperate areas. A chemotaxonomic discussion on the distribution of each compound among single or different types of microorganisms, either phylogenetically related or unrelated species, is included.

Voucher-based reinforcement of cocaine abstinence in treatment-resistant methadone patients: effects of reinforcement magnitude.

Voucher-based reinforcement of cocaine abstinence has been one of the most effective means of treating cocaine abuse in methadone patients, but it has not been effective in all patients. This study was designed to determine if we could promote cocaine abstinence in a population of treatment-resistant cocaine abusing methadone patients by increasing the magnitude of voucher-based abstinence reinforcement. Participants were 29 methadone patients who previously failed to achieve sustained cocaine abstinence when exposed to an intervention in which they could earn up to $1155 in vouchers (exchangeable for goods/services) for providing cocaine-free urines. Each patient was exposed in counterbalanced order to three 9-week voucher conditions that varied in magnitude of voucher reinforcement. Patients were exposed to a zero, low and high magnitude condition in which they could earn up to $0, $382, or $3480 in vouchers for providing cocaine-free urines. Analyses for 22 patients exposed to all three conditions showed that increasing voucher magnitude significantly increased patients' longest duration of sustained cocaine abstinence (P<0.001) and percent of cocaine-free urines (P<0.001), and significantly decreased patients' reports of cocaine injections (P=0.024). Almost half (45%) of the patients in the high magnitude condition achieved >/=4 weeks of sustained cocaine abstinence, whereas only one patient in the low and none in the zero magnitude condition achieved more than 2 weeks. Reinforcement magnitude was a critical determinant of the effectiveness of this abstinence reinforcement intervention.

Isolation and characterization of novel human immunodeficiency virus integrase inhibitors from fungal metabolites.

We have identified a series of novel inhibitors of human immunodeficiency virus type 1 (HIV-1) integrase by randomly screening natural product extracts using an in vitro biochemical assay designed to identify inhibitors of integrase-catalysed strand transfer. Equisetin recovered from the fungus Fusarium heterosporum and a novel enantiomeric homologue of equisetin from Phoma sp. were isolated as inhibitors of HIV-1 integrase in vitro. Two additional analogues, a novel decalin derivative, integric acid, and oteromycin were also discovered to be inhibitors of integrase. Equisetin and related compounds inhibit 3' end-processing and strand transfer as well as disintegration catalysed by either the full-length enzyme or the truncated integrase core domain (amino acids 50-212). These compounds also inhibit strand transfer reactions catalysed by stable complexes assembled in vitro and integration reactions catalysed by pre-integration complexes isolated from HIV-1-infected cells. The compounds described in this report are structurally novel and mechanistically distinct from many previously described inhibitors of HIV-1 integrase. These results demonstrate the utility of using an appropriately configured assay to identify compounds that are effective post-assembly and the potential of isolating novel integrase inhibitors from complex natural product extracts.

Contingent reinforcement sustains post-detoxification abstinence from multiple drugs: a preliminary study with methadone patients.

This study examined the efficacy of a urinalysis-based contingency management program for preventing relapse to abused drugs following a brief residential detoxification. Fourteen methadone maintenance patients who were chronic benzodiazepine users were enrolled in a 7-day inpatient benzodiazepine detoxification and randomly assigned to receive Contingency Management (N = 7) or Standard Care (N = 7) therapy upon return to outpatient methadone treatment. In the Contingency Management condition, a methadone take-home dose or a US $25 voucher (patient's choice) could be earned for each urine sample submitted on a Monday, Wednesday or Friday that was free of opiates, cocaine and benzodiazepines. Data analysis and interpretation focused on within-group post-hoc differences due to group differences on employment and legal status, potentially confounding baseline variables. Repeated measures analysis of variance showed that Contingency Management patients submitted significantly more drug-free urine samples during the intervention compared to pre-detoxification (p < 0.01), whereas no significance changes were observed from pre- to post-detoxification in the Standard Care patients. Employment and legal status of patients may have facilitated response to contingency management procedures, but did not prevent relapse when contingency management procedures were withdrawn. Overall, these preliminary results suggest that abstinence-based contingency management is a promising strategy for preventing relapse to multiple drugs of abuse in a subset of methadone maintenance patients when abstinence has been initiated through brief inpatient treatment.