Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

This review surveys advances in the literature that impact organic sacrificial electron donor recycling in artificial photosynthesis. Systems for photocatalytic carbon dioxide reduction are optimized using sacrificial electron donors. One strategy for coupling carbon dioxide reduction and water oxidation to achieve artificial photosynthesis is to use a redox mediator, or recyclable electron donor. This review highlights photo- and electrochemical methods for recycling amines and NADH analogues that can be used as electron donors in artificial photosynthesis. Important properties of sacrificial donors and recycling strategies are also discussed. Compounds from other fields, such as redox flow batteries and decoupled water splitting research, are introduced as alternative recyclable sacrificial electron donors and their oxidation potentials are compared to the redox potentials of some model photosensitizers. The aim of this review is to act as a reference for researchers developing photocatalytic systems with sacrificial electron donors, and for researchers interested in designing new redox mediator and recyclable electron donor species.

Stabilization of Polyoxometalate Charge Carriers via Redox-Driven Nanoconfinement in Single-walled Carbon Nanotubes

We describe the preparation of hybrid redox materials based on polyoxomolybdates encapsulated within single-walled carbon nanotubes (SWNTs). Polyoxomolybdates readily oxidize SWNTs under ambient conditions in solution, and here we study their charge-transfer interactions with SWNTs to provide a detailed mechanistic insight into the redox-driven encapsulation of these - and similar - nanoclusters. We are able to correlate the relative redox potentials of the encapsulated clusters with the level of SWNT oxidation in the resultant hybrid materials and use this to show that precise redox tuning is a necessary requirement for successful encapsulation. The host-guest redox materials described here exhibit exceptional electrochemical stability, retaining up to 86% of their charge capacity over 1000 oxidation/reduction cycles despite the typical lability and solution-phase electrochemical instability of the polyoxomolybdates we have explored. Our findings illustrate the broad applicability of the redox-driven encapsulation approach to the design and fabrication of tunable, highly conductive, ultra-stable nanoconfined energy materials.

Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst

Despite their technological importance for water splitting, the reaction mechanisms of most water oxidation catalysts (WOCs) are poorly understood. This paper combines theoretical and experimental methods to reveal mechanistic insights into the reactivity of the highly active molecular manganese vanadium oxide WOC [Mn4V4O17(OAc)3]3- in aqueous acetonitrile solutions. Using density functional theory together with electrochemistry and IR-spectroscopy, we propose a sequential three-step activation mechanism including a one-electron oxidation of the catalyst from [Mn2 3+Mn2 4+] to [Mn3+Mn3 4+], acetate-to-water ligand exchange, and a second one-electron oxidation from [Mn3+Mn3 4+] to [Mn4 4+]. Analysis of several plausible ligand exchange pathways shows that nucleophilic attack of water molecules along the Jahn-Teller axis of the Mn3+ centers leads to significantly lower activation barriers compared with attack at Mn4+ centers. Deprotonation of one water ligand by the leaving acetate group leads to the formation of the activated species [Mn4V4O17(OAc)2(H2O)(OH)]- featuring one H2O and one OH ligand. Redox potentials based on the computed intermediates are in excellent agreement with electrochemical measurements at various solvent compositions. This intricate interplay between redox chemistry and ligand exchange controls the formation of the catalytically active species. These results provide key reactivity information essential to further study bio-inspired molecular WOCs and solid-state manganese oxide catalysts.

Molecular Vanadium Oxides for Energy Conversion and Energy Storage: Current Trends and Emerging Opportunities

Molecular vanadium oxides, or polyoxovanadates (POVs), have recently emerged as a new class of molecular energy conversion/storage materials, which combine diverse, chemically tunable redox behavior and reversible multielectron storage capabilities. This Review explores current challenges, major breakthroughs, and future opportunities in the use of POVs for energy conversion and storage. The reactivity, advantages, and limitations of POVs are explored, with a focus on their use in lithium and post-lithium-ion batteries, redox-flow batteries, and light-driven energy conversion. Finally, emerging themes and new research directions are critically assessed to provide inspiration for how this promising materials class can advance research in sustainable energy technologies.

Host-Guest Hybrid Redox Materials Self-Assembled from Polyoxometalates and Single-Walled Carbon Nanotubes

The development of next-generation molecular-electronic, electrocatalytic, and energy-storage systems depends on the availability of robust materials in which molecular charge-storage sites and conductive hosts are in intimate contact. It is shown here that electron transfer from single-walled carbon nanotubes (SWNTs) to polyoxometalate (POM) clusters results in the spontaneous formation of host-guest POM@SWNT redox-active hybrid materials. The SWNTs can conduct charge to and from the encapsulated guest molecules, allowing electrical access to >90% of the encapsulated redox species. Furthermore, the SWNT hosts provide a physical barrier, protecting the POMs from chemical degradation during charging/discharging and facilitating efficient electron transfer throughout the composite, even in electrolytes that usually destroy POMs.

Capgras syndrome presenting in an adolescent girl in the Caribbean

The case of a 16-year old Jamaican girl who presented to the psychiatric service of a general hospital with features of Capgras syndrome is presented. Her history, treatment, progress and relevant psychodynamic and neurocognitive issues are explored. This is the first known published case of an adolescent with Capgras syndrome from the Caribbean. The case highlights that the syndrome may occur in different cultural contexts and that clinicians should be sensitive to its existence in order to avert under-diagnosis or misdiagnosis.

Validation of the Beck Depression Inventory II in HIV-positive patients

OBJECTIVE

Research on depression among HIV-positive patients has been limited by the lack of a valid and reliable measure of depression. This project addresses this problem by exploring the internal consistency reliability and the concurrent and discriminant validity of the Beck Depression Inventory-II (BDI-II) using HIV-positive patients in Jamaica.

METHOD

Patients from three HIV clinics in Jamaica (n = 191 patients; 61% female, 39% male, mean age 40.5-10 years) were administered the BDI-II along with the Centre for Epidemiological Studies -Depression Scale (CES-D) and the Social Provisions Scale.

RESULTS

Overall, the BDI-II was found to have a high degree of reliability (alpha = 0.89). The scale also had good concurrent validity as evidenced by a high correlation with scores on the CES-D (r = 0.74) and acceptable discriminant validity as demonstrated through a moderate correlation with the Social Provisions Scale (r = -0.42). This pattern of scores suggests that the majority of the variance underlying the BDI-II assesses depression (55%) while a smaller degree of the variability (18%) measures a conceptually similar but distinct concept.

CONCLUSION

The BDI-II is a sufficiently reliable and valid measure for assessing depression in HIV-positive patients.

Patterns of depressive symptoms among patients with HIV infection

OBJECTIVE

To identify the level of depressive symptoms among patients with HIV infection and to examine the reported patterns of depressive symptoms not confounded by the physical manifestations of HIV-infection.

METHOD

A total of 191 patients with HIV infection (75 males (39%) and 116 females (61%), mean age 40.48 +/- 10 years), from three HIV clinics were administered the Beck Depression Inventory-II as well as a demographic questionnaire as part of a larger study.

RESULTS

Moderate to severe depressive symptoms were reported by 17.3% of the HIV-infected patients with females reporting significantly higher levels of depressive symptoms than males. A principal components analysis identified three clusters of depressive symptoms: cognitive-affective, negative cognitions and somatic symptoms. The HIV-infected patients were found to display mainly cognitive-affective symptoms of depression.

CONCLUSION

HIV-infected patients, especially female patients, may be at an increased risk of experiencing high levels of depressive symptoms. It is recommended that HIV-infected patients be routinely screened for depression, particularly cognitive-affective symptoms of depression.

Factors associated with depression in students at The University of the West Indies, Mona, Jamaica

OBJECTIVE

This project examines the factors associated with depression in students attending the University of the West Indies, Mona Campus.

METHOD

Students enrolled in the Foundation courses during the first and second semesters of the 2005/2006 academic year were administered the Brief Screen for Depression as well as a demographic questionnaire as part of a larger study.

RESULTS

A wide cross-section of the university population was sampled (n = 690; 252 from semester one, 438 from semester two; 77% females, 23% males; age 16-62 years, median = 20 years, mean = 23.4 years +/- 7.4). Nearly 40% of students scored in the clinically depressed range. Students in the December wave of data collection had higher depression scores than those in the January wave. Consistent with international research, females reported significantly higher levels of depressive symptoms. Married students reported significantly lower depression scores than students in visiting relationships. Students who were combining employment and school reported lower depression scores than those who were not employed. Maternal education significantly influenced students' levels of depression such that students whose mothers had university or other tertiary education had lower depression scores while those whose mothers had primary or lower education had the highest depression scores. Students with a chronic condition or a disability scored higher than those without such problems on all three measures of depression.

CONCLUSION

Depression may be a significant problem in students at The University of the West Indies, Mona campus.

HIV infection, sexual abuse and social support in Jamaican adolescents referred to a psychiatric service

BACKGROUND

Children and adolescents with HIV/AIDS often have psychological/psychiatric issues that require specialist intervention. We explored whether HIV infection acquired through sexual abuse led to particularly negative psychiatric outcomes and whether good social support is a protective factor in the development of undesirable psychiatric sequelae.

METHODS

This study consists of a case series of five persons referred from the Paediatric Infectious Diseases Clinic to the Child Psychiatry Clinic, both at the University Hospital of the West Indies (UHWI) in Jamaica, during July 1 to November 30, 2005. The patients were clinically assessed and diagnosed by a psychiatrist using the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition (DSM IV) criteria. Cases were compared according to gender, age, likely route of HIV infection, level offamily/social support and nature of psychiatric outcome.

RESULTS

Adolescents who acquired HIV infection through sexual abuse reported more intense feelings of sadness and suicidal ideations. Those with good social support reported less intense feelings of sadness with no suicidal ideations and were more optimistic about their future regardless of the route of acquisition. Two of three adolescents who acquired HIV infection through sexual abuse and one of two who was perinatally infected required ongoing supportive psychotherapy to augment their social support, the characteristic most associated with favourable outcome.

CONCLUSION

Both sexual abuse and HIV/AIDS are likely to have negative psychological consequences in children and adolescents. This psychological impact may be intensified when HIV infection results from sexual assault as opposed to other methods of transmission. The findings support the practice of providing HIV prophylaxis to all sexual assault victims of known or suspected HIV-positive perpetrators and of encouraging utilization of existing social support networks.

Validation of the Brief Screen for Depression in a Jamaican cohort

Research on depression in Jamaicans has been limited by the absence of a psychometrically sound measure of depression. This project attempts to rectify this problem by exploring the concurrent and discriminant validity of the Brief Screen for Depression (BSD) using a sample of 244 students attending the University of the West Indies, Mona, Jamaica. Participants were administered the BSD along with the Beck Depression Inventory (BDI), the Center for Epidemiologic Studies Depression scale (CES-D) the University of California at Los Angeles (UCLA) Loneliness Scale - Revised, (UCLA-R) and the Responding Desirably on Attitudes and Opinions scale (RD16). Overall, the BSD was found to have an acceptable level of concurrent validity as evidenced by high correlations with scores on the BDI (0.64) and the CES-D (0.62), and an acceptable level of discriminant validity as demonstrated through moderate correlations with the UCLA Loneliness Scale (0.40). In addition, the BSD was found to possess a moderate degree of sensitivity in identifying individuals who may be experiencing clinically significant symptoms of depression.

Validation of the beck depression inventory-II in a Jamaican university student cohort

OBJECTIVE

This project explores the internal consistency reliability and the concurrent and discriminant validity of the Beck Depression Inventory-II (BDI-II) using a wide cross-section of the student population attending the University of the West Indies, Kingston, Jamaica.

SUBJECTS AND METHODS

Students enrolled in UWI Foundation courses during the first and second semesters of the 2005/2006 academic year (n = 690; 77% females, 23% males; mean age = 23.4 +/- 7.4 years) were administered the BDI-II along with the Brief Screen for Depression (BSD), the Centre for Epidemiological Studies--Depression Scale (CES-D) and the UCLA Loneliness Scale--Revised.

RESULTS

Overall, the BDI-II was found to have an acceptable degree of reliability (alpha = 0.90). The scale also had reasonably good concurrent validity as evidenced by high correlations with scores on the BSD (r = 0.74) and the CES-D (r = 0.71) and acceptable discriminant validity as demonstrated through moderate correlations with the UCLA Loneliness Scale (r = 0.50). This pattern of scores suggests that the majority of the variance underlying the BDI-II assesses depression (50% to 55%) while a smaller degree of the variability (25%) measures a conceptually similar but distinct concept.

CONCLUSION

The BDI-II is a reliable and valid measure for assessing depression within the Jamaican population.

Depression in adolescence: new developments

Depression in adolescence is under-recognized although its associated burden of illness is very high. Some frequent associations with depression in this age group are under-achievement, poor lifestyle choices including substance abuse, and a high risk of the persistence of the illness into adulthood There is also an increased risk of mortality related to suicide and harmful lifestyles. For depression in adolescents to be reduced, there needs to be strong collaboration among health professions, adolescents and their caregivers. Non-mental health clinicians must expand their role and become better prepared to recognize, prevent and treat depression in this age-group. Greater public awareness must also be achieved so that adolescents and their caregivers can seek help early.

Screening for postpartum depression

Postpartum depression, a potentially serious public health problem can be effectively treated. With the implementation of universal screening with a standardized, self-administered screening tool, in conjunction with appropriate education and training of health care providers to increase awareness of this problem and to impart greater diagnostic suspicion, identification of and early intervention for PPD can be facilitated. There is need for increased collaboration between Obstetric and Consultation Liaison Psychiatric Services, with particular emphasis on the prevention of psychiatric morbidity associated with pregnancy, thereby improving the quality of life for and interaction between mother and child. The establishment of a true Liaison Psychiatric Service dedicated to pregnancy and the postpartum period, with a Psychiatrist employed by the Obstetric Services, may be of great value.

Field potentials in the olfactory bulb of the rainbow trout (Salmo gairdneri): evidence for a dendrodendritic inhibitory pathway

Field potentials have been recorded from the olfactory bulb of the teleost fish, Salmo gairdneri. Stimulation of the olfactory nerve generates a complex wave pattern, which when recorded near the surface in the centre of the bulb consists of one positive and three negative components, P, N1, N2 and N3. The N1 has been attributed to depolarization of mitral cell dendrites, N2 to depolarization of the superficial dendrites of granules cells, and P to subsequent hyperpolarization of mitral cells. Possible origins of the N3 wave are discussed. Spikes from single units recorded in the mitral cell layer usually occur superimposed on the N1 wave, and single units recorded in the region of granule cells are usually found coincident with the trailling edge of the deep positive wave. With the exception of N3 the patterns of activity observed are very similar to previously published results obtained from other vertebrates. It is suggested that the dendrodendritic inhibitory pathway proposed for the mammalian olfactory bulb (Rall et al., 1966; Rall and Shepherd, 1968) is common to all vertebrates.

On the ultrastructure and permeability of taste buds of the marine teleost Ciliata mustela

The abundant taste buds of the barbels and free fin rays of the five bearded rockling, Ciliata mustela contain an average of 100-150 cells, falling into two types. Tubule-containing cells ('t-cells'), tentatively identified as receptor cells, and each surrounded by fibril-containing cells ('f-cells') in the central part of the bud. t-Cells also occur in two concentric shells separated by indifferent epithelial cells at the periphery of the bud. f-Cells are characterized by their concentrations of fine fibrils, and by granules or vesicles of 180-190 mmu diameter. The 100 or so receptor cells in a taste bud are innervated by some 250 axons. Lanthanum penetrates more deeply into the extracellular space of taste buds than into the extracellular space of the general epithelium, perhaps indicating that a greater area than the mere protruding tip of receptor cells may be accessible to chemical stimulation. Degenerating cells may provide an important route of entry for such external agents.