Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 24
Filter
1.
Article in English | MEDLINE | ID: mdl-38523702

ABSTRACT

Objective: Both the therapeutic alliance and the specific skills taught in treatment are thought to contribute to change in cognitive-behavior therapy (CBT), but it is unclear if or how these processes influence each other and outcomes in treatment. We tested the hypothesis that the degree to which patients used CBT skills would mediate the relation between the alliance and session-to-session changes in anxiety and depression. Method: Adult participants (N = 70; Mage = 33.74, 67% female, 70% White) with emotional disorders were randomized to receive 6 or 12 sessions of the Unified Protocol. Before each session, participants reported anxiety and depression severity and past-week skillfulness. After each session, participants rated the strength of the alliance. We tested whether greater within-person skillfulness mediated the relation between within-person alliance strength and session-to-session changes in anxiety and depression. Results: Skillfulness significantly mediated the effect of the alliance on session-to-session changes in anxiety, ab = -.02, p = .04, and depression, ab = -.02, p = .02, such that a stronger alliance predicted greater next-session skillfulness, which predicted session-to-session decreases in anxiety and depression. When alliance subscales were examined separately, the strongest effect was observed for agreement on therapy tasks. Conclusions: Improvements in the alliance may facilitate skill use and indirectly predict reductions in anxiety and depression through skill use in CBT. We encourage research on how to enhance both the alliance and skillfulness in CBT.

2.
Article in English | MEDLINE | ID: mdl-37900357

ABSTRACT

Although cross-sectional research highlights similarities between symptoms of obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD) among individuals exposed to sexual trauma, little is known about how these disorders relate over time. The goal of the present study was to examine whether 1) OCD symptoms prospectively predicted daily symptoms of PTSD, and 2) OCD and PTSD symptoms prospectively predicted daily experiences of sexual trauma-related mental contamination (i.e., dirtiness in the absence of a physical pollutant). Forty-one women with a sexual trauma history completed baseline measures of OCD and PTSD, as well as twice-daily assessments of PTSD symptoms and mental contamination over a two-week period. Total OCD symptoms and the unacceptable thoughts dimension significantly predicted daily PTSD symptoms after accounting for other OCD dimensions. Only total OCD symptoms significantly predicted daily mental contamination when examined together with total PTSD symptoms. No individual PTSD or OCD clusters/dimensions significantly predicted daily mental contamination when examined simultaneously. Findings from this study highlight the nuanced associations among OCD symptoms, PTSD symptoms, and experiences of mental contamination. Future research is needed to further understand the development of PTSD, OCD, and mental contamination over time to inform targets for intervention.

3.
J Trauma Stress ; 36(5): 932-942, 2023 Oct.
Article in English | MEDLINE | ID: mdl-37653683

ABSTRACT

Mental contamination refers to feelings of dirtiness in response to thoughts, images, or memories. Mental contamination is frequently reported after sexual trauma and is associated with symptoms of posttraumatic stress disorder (PTSD). Differences in individuals' views about morality and purity may influence the severity of mental contamination, though this has been studied primarily outside of samples assessed for trauma and/or PTSD. The present study addressed this gap by investigating scrupulosity as a prospective predictor of daily sexual trauma-related mental contamination and PTSD symptoms. Participants included 40 adult women with a history of sexual trauma and current sexual trauma-related mental contamination who completed baseline diagnostic interviews and questionnaires followed by two assessments every day for 2 weeks. The results indicate that scrupulosity was positively correlated with PTSD symptom severity and sexual trauma-related mental contamination at baseline. Scrupulosity was also a prospective predictor of increased daily sexual trauma-related mental contamination, B = 0.19, SE = 0.07, p = .010, but not daily PTSD symptoms, B = -0.10, SE = .08, p = .198. The findings indicate that scrupulosity may be an important factor in understanding recovery from sexual assault.

4.
J Interpers Violence ; 38(19-20): 11117-11137, 2023 10.
Article in English | MEDLINE | ID: mdl-37386852

ABSTRACT

Mental contamination (MC), the experience of dirtiness in the absence of a physical contaminant, has established links with posttraumatic stress disorder (PTSD). Shame and guilt have well-documented relationships with symptoms of PTSD and may play a role in the development and maintenance of MC. The present study examined whether trauma-related shame and guilt prospectively predicted daily MC and symptoms of PTSD among 41 women with a history of sexual trauma. Women completed baseline and twice-daily assessments of MC and symptoms of PTSD over a 2-week period and baseline measures of trauma-related shame and guilt. Two sets of hierarchical mixed linear regression models examined individual and combined fixed effects of baseline trauma-related guilt (guilt cognitions and global guilt) and shame in predicting daily trauma-related MC and symptoms of PTSD. Trauma-related shame positively predicted both daily MC and PTSD. This association remained robust even when accounting for the experience of trauma-related guilt. Neither trauma-related guilt cognitions nor global guilt predicted daily MC or PTSD. While other studies have addressed shame related to sexual assault, this is the first study to demonstrate a positive prospective relationship between shame and trauma-related MC. Findings regarding PTSD and shame are consistent with a growing literature. Further research is needed to better understand the temporal relationships between trauma-related shame, MC, and symptoms of PTSD, including how these variables interact and change over the course of PTSD treatment. A better understanding of the factors influencing the development and maintenance of MC can inform efforts to more easily target and improve MC, and subsequently PTSD.


Subject(s)
Stress Disorders, Post-Traumatic , Humans , Female , Stress Disorders, Post-Traumatic/diagnosis , Guilt , Shame , Survivors , Sexual Trauma
5.
Psychol Trauma ; 15(3): 367-376, 2023 Mar.
Article in English | MEDLINE | ID: mdl-35901427

ABSTRACT

OBJECTIVE: Posttraumatic stress disorder (PTSD) and nonmedical prescription opioid use (NMPOU) are linked. Much of the research documenting this association uses cross-sectional or longitudinal designs that describe patterns of use over extended intervals. The present study used a daily monitoring design to examine how daily fluctuations in PTSD symptoms predicted patterns of prescription opioid use (both medical and nonmedical) and co-use of other substances. This approach has distinct advantages for understanding proximal temporal relations between PTSD symptom variation and substance use patterns. METHOD: Forty adults with clinical or subclinical PTSD and past-month NMPOU completed daily measures of PTSD symptoms, physical pain, prescription opioid use, and other substance use for 28 days using a smartphone application. RESULTS: Same day co-use of prescription opioids and at least one other substance was common. Higher-than-typical PTSD symptoms on a given day (within-person) was associated with an increased likelihood of reporting NMPOU (overall and with co-use of one or more additional substances) on the same day. This association was specific to PTSD alterations in arousal and reactivity symptoms (Criteria E). Neither total PTSD symptoms nor individual PTSD symptom clusters prospectively predicted next-day prescription opioid use (overall or with co-use). Use of prescription opioids also did not predict next-day PTSD symptom severity. CONCLUSION: This is the first study to demonstrate positive associations between day-to-day fluctuations in PTSD symptoms and NMPOU. Results from the current study also highlight the importance of examining polysubstance use patterns among individuals with PTSD who use prescription opioids. (PsycInfo Database Record (c) 2023 APA, all rights reserved).


Subject(s)
Opioid-Related Disorders , Stress Disorders, Post-Traumatic , Adult , Humans , Stress Disorders, Post-Traumatic/epidemiology , Analgesics, Opioid/therapeutic use , Cross-Sectional Studies , Opioid-Related Disorders/epidemiology , Opioid-Related Disorders/drug therapy , Prescriptions
6.
J Anxiety Disord ; 86: 102517, 2022 03.
Article in English | MEDLINE | ID: mdl-34973537

ABSTRACT

Mental contamination (MC) - dirtiness experienced in the absence of contact with a physical contaminant - has been linked to PTSD symptoms following sexual trauma. However, there is limited understanding regarding the temporal nature of this association. The present study utilized experience sampling to examine associations between baseline and daily experiences of MC and PTSD symptoms and the mediating role of avoidance and approach coping among a sample of 41 adult women with a history of sexual trauma and current MC. Participants completed baseline measures and 14 days of twice-daily assessments. Results indicated that daily MC and PTSD symptoms were bidirectionally related. The tendency to engage in avoidance coping positively mediated relations between 1) baseline MC and daily PTSD symptoms and 2) baseline PTSD symptoms and daily MC. Further, daily avoidance coping (T-1) positively mediated associations between daily MC (T-2) and subsequent daily PTSD symptoms (T). Approach coping was not a mediator (between- or within-) in any models. Findings lend support to a mutual maintenance model of PTSD symptoms and trauma-related MC mediated by avoidance coping. Future research over a more extended period is warranted to clarify whether PTSD symptoms and MC indeed mutually maintain or exacerbate one another over time.


Subject(s)
Stress Disorders, Post-Traumatic , Adaptation, Psychological , Adult , Female , Humans , Sexual Trauma , Stress Disorders, Post-Traumatic/diagnosis
7.
AIDS Care ; 33(3): 311-315, 2021 03.
Article in English | MEDLINE | ID: mdl-31931621

ABSTRACT

Persons living with HIV (PLWH) are significantly more likely to meet criteria for a psychiatric disorder compared to the general population. To our knowledge there are no prior studies that report rates of psychiatric diagnosis documentation in electronic medical records (EMRs) of PLWH. The goal for this study was to report the rates of a variety of psychiatric diagnoses among PLWH in electronic medical records. Participants (n = 2,336) were enrolled in the Center for AIDS Research (CFAR) Longitudinal Database study at the University of Pennsylvania, Philadelphia, PA. Diagnostic codes were extracted from the EMR for depressive disorders, alcohol and substance use disorders, PTSD, sleep disorders, and adjustment disorders and were compared to rates from national epidemiological studies. Rates of Major Depressive Disorder in the EMR were comparable to prior reports on HIV-infected samples. In contrast, rates of PTSD, substance use disorders, alcohol use disorders, adjustment disorders and insomnia from the EMR were all markedly lower compared to national estimates for HIV-infected samples. While clinicians appropriately documented evidence of Major Depressive Disorder, other psychiatric comorbidities were largely overlooked. These findings suggest a potential bias in how clinicians either detect or document psychiatric disorders in PLWH.


Subject(s)
Documentation/statistics & numerical data , Electronic Health Records/statistics & numerical data , HIV Infections/epidemiology , Mental Disorders/epidemiology , Adult , Aged , Alcoholism/epidemiology , Comorbidity , Depressive Disorder/epidemiology , Depressive Disorder/etiology , Depressive Disorder/psychology , Depressive Disorder, Major/epidemiology , Depressive Disorder, Major/etiology , Depressive Disorder, Major/psychology , Female , HIV Infections/psychology , Humans , Male , Mental Disorders/psychology , Middle Aged , Philadelphia/epidemiology , Stress Disorders, Post-Traumatic/epidemiology , Stress Disorders, Post-Traumatic/etiology , Stress Disorders, Post-Traumatic/psychology
8.
Cogn Behav Ther ; 50(2): 121-137, 2021 03.
Article in English | MEDLINE | ID: mdl-32835597

ABSTRACT

Perfectionistic cognitions are thinking patterns that reflect excessive striving and are associated with emotional disorders in nonclinical samples. Despite literature connecting trait perfectionism with psychological disorders, much remains unknown about how perfectionistic cognitions relate to anxiety disorder symptoms in clinical populations. This is the first study to our knowledge that investigates how symptoms of anxiety and related symptoms are influenced by the frequency of perfectionistic cognitions when controlling for well documented correlates of anxiety. Perfectionistic cognitions, depressive symptoms, emotion regulation, anxiety sensitivity, and anxiety symptom severity were assessed prior to starting treatment in 356 treatment-seeking patients diagnosed with an anxiety or anxiety-related disorder at a specialty anxiety clinic. Perfectionistic cognitions were significantly correlated with all anxiety symptom measures as well as measures of depression, emotion regulation and anxiety sensitivity (range of rs =.22-.68). Hierarchical regression analyses revealed that when controlling for depressive symptoms, anxiety sensitivity, and emotion regulation, perfectionistic cognitions significantly and uniquely contribute to the variance of GAD (p <.01) and PTSD (p <.05) symptoms but not other anxiety-related symptoms (all ps >.05). Regardless of specific diagnoses, treatment-seeking individuals reporting frequent perfectionistic thoughts are more likely to report more severe symptoms of PTSD and GAD.


Subject(s)
Anxiety Disorders/psychology , Anxiety Disorders/therapy , Cognition , Perfectionism , Adolescent , Adult , Aged , Anxiety Disorders/diagnosis , Humans , Middle Aged , Young Adult
9.
AIDS Care ; 33(5): 616-622, 2021 05.
Article in English | MEDLINE | ID: mdl-32741212

ABSTRACT

Persons living with HIV (PLWH) are significantly more likely to die by suicide compared to the general population. This is the first study to examine the impact of posttraumatic stress disorder (PTSD), major depressive disorder (MDD), insomnia, and substance use disorders on suicidal ideation/behavior among PLWH using electronic medical record (EMR) data. We also evaluated the mutual influence of interactions between PTSD and substance use disorders on suicide risk, consistent with the substance abuse, violence exposure, and HIV/AIDS "SAVA" syndemic model. Participants (n = 2336) were HIV+ individuals recruited through the Center for AIDS Research (CFAR). Participants provided informed consent for extraction of their EMR. As hypothesized, univariate analyses revealed that PTSD, MDD, insomnia, alcohol and other substance use disorders (cocaine abuse and cocaine dependence, opioid abuse and dependence, cannabis abuse, other psychoactive substance abuse and dependence, and polysubstance use disorder) were each positively associated with suicidal ideation/behavior. Also as hypothesized, a multivariable analysis found that alcohol and cocaine dependence, MDD, and PTSD were significant predictors of suicidal ideation/behavior. Contrary to hypotheses, none of the interactions between PTSD and substance use disorders were significantly associated with suicidal ideation/behavior.


Subject(s)
Depressive Disorder, Major , HIV Infections , Stress Disorders, Post-Traumatic , Suicide , Depressive Disorder, Major/epidemiology , HIV Infections/epidemiology , Humans , Risk Factors , Stress Disorders, Post-Traumatic/epidemiology , Suicidal Ideation , Suicide, Attempted
10.
J Affect Disord ; 267: 86-95, 2020 04 15.
Article in English | MEDLINE | ID: mdl-32063577

ABSTRACT

BACKGROUND: Numerous randomized controlled trials (RCTs) have examined the efficacy of cognitive behavioral therapy (CBT) in reducing anxiety symptoms. However, relatively fewer studies have examined the effectiveness of CBT in naturalistic treatment settings. There is even less known about the mechanisms underlying successful outcomes in naturalistic samples receiving CBT. This study aimed to examine the absolute and relative mediation of emotion regulation (ER) difficulties and anxiety sensitivity (AS) on anxiety symptom reduction. METHODS: Participants were treatment-seeking patients (N = 247) at an outpatient anxiety clinic. Measures of difficulties in ER, AS, and disorder specific symptoms were administered at baseline, mid, and post-treatment. A composite anxiety score was calculated to measure anxiety disorder symptom severity across anxiety-related diagnoses. RESULTS: Individual mediation models revealed that both AS and ER significantly mediated the reduction in anxiety-related symptoms over the course of treatment. A multiple mediation model found that ER was the strongest mediator (indirect effect = -1.030, 95% CI = -2.172 to -0.153). Further analyses revealed that the ER subscale of impulse control difficulties (e.g., the tendency to avoid when confronted with a feared stimulus) was the strongest mediator (indirect effect = -0.849, 95% CI = -1.913 to -0.081). LIMITATIONS: This study relied solely on self-report measures of ER, AS, and anxiety pathology, and did not have a control group. CONCLUSIONS: These results suggest that improvement in the ability to control impulses may act as a mechanism of anxiety symptom reduction and may be important to target in CBT with naturalistic samples.


Subject(s)
Cognitive Behavioral Therapy , Emotional Regulation , Anxiety/therapy , Anxiety Disorders/therapy , Fear , Humans , Treatment Outcome
11.
Ophthalmic Surg Lasers Imaging Retina ; 50(3): 187-191, 2019 03 01.
Article in English | MEDLINE | ID: mdl-30893454

ABSTRACT

The authors report a case of nonconforming focal choroidal excavation (FCE) identified in an eye following blunt, nonperforating trauma to the globe. Multimodal imaging was undertaken including color fundus photographs, enhanced depth imaging optical coherence tomography, fluorescein angiography, and fundus autofluorescence. This shows that FCE may result from blunt ocular trauma. The authors hypothesize that loss of structural support provided by an intact Bruch's membrane may be a key factor in precipitating the specific morphological changes associated with FCE occurring in a range of clinical settings. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:187-190.].


Subject(s)
Choroid Diseases/etiology , Eye Injuries/complications , Adult , Humans , Male , Vision Disorders/etiology
12.
Retin Cases Brief Rep ; 11(4): 361-363, 2017.
Article in English | MEDLINE | ID: mdl-28922308

ABSTRACT

PURPOSE: To report a giant retinal pigment epithelium rip in a patient with a bullous retinal and choroidal detachment. METHODS: Case report with widefield imaging, fundus autofluorescence, and optical coherence tomography of the retina. RESULTS: This 62-year-old patient had a history of advanced glaucoma, trabeculectomy, blebitis, and endophthalmitis. He had cataract surgery 6 weeks before presentation. He was found to have a large bullous retinal and choroidal detachment with a large retinal pigment epithelium tear at the limit of the choroidal detachment. After vitrectomy for retinal detachment repair, the tear was observed to extend inferiorly at the margins of the choroidal detachment. CONCLUSION: This case report demonstrates that large retinal pigment epithelium rips can be found associated with large bullous choroidal and retinal detachments. These tears seem similar to tears that have been observed after trabeculectomy.


Subject(s)
Choroid Diseases/complications , Retinal Detachment/complications , Retinal Perforations/etiology , Humans , Male , Middle Aged
13.
Ophthalmology ; 123(11): 2352-2367, 2016 11.
Article in English | MEDLINE | ID: mdl-27523615

ABSTRACT

PURPOSE: To determine if the area of the foveal avascular zone (FAZ) is correlated with visual acuity (VA) in diabetic retinopathy (DR) and retinal vein occlusion (RVO). DESIGN: Cross-sectional study. PARTICIPANTS: Ninety-five eyes of 66 subjects with DR (65 eyes), branch retinal vein occlusion (19 eyes), and central retinal vein occlusion (11 eyes). METHODS: Structural optical coherence tomography (OCT; Spectralis, Heidelberg Engineering) and OCT angiography (OCTA; Avanti, Optovue RTVue XR) data from a single visit were analyzed. FAZ area, point thickness of central fovea, central 1-mm subfield thickness, the occurrence of intraretinal cysts, ellipsoid zone disruption, and disorganization of retinal inner layers (DRIL) length were measured. VA was also recorded. Correlations between FAZ area and VA were explored using regression models. Main outcome measure was VA. RESULTS: Mean age was 62.9±13.2 years. There was no difference in demographic and OCT-derived anatomic measurements between branch retinal vein occlusion and central retinal vein occlusion groups (all P ≥ 0.058); therefore, data from the 2 groups were pooled together to a single RVO group for further statistical comparisons. Univariate and multiple regression analysis showed that the area of the FAZ was significantly correlated with VA in DR and RVO (all P ≤ 0.003). The relationship between FAZ area and VA varied with age (P = 0.026) such that for a constant FAZ area, an increase in patient age was associated with poorer vision (rise in logarithm of the minimum angle of resolution visual acuity). Disruption of the ellipsoid zone was significantly correlated with VA in univariate and multiple regression analysis (both P < 0.001). Occurrence of intraretinal cysts, DRIL length, and lens status were significantly correlated with VA in the univariate regression analysis (P ≤ 0.018) but not the multiple regression analysis (P ≥ 0.210). Remaining variables evaluated in this study were not predictive of VA (all P ≥ 0.225). CONCLUSIONS: The area of the FAZ is significantly correlated with VA in DR and RVO and this relationship is modulated by patient age. Further study about FAZ area and VA correlations during the natural course of retinal vascular diseases and following treatment is warranted.


Subject(s)
Diabetic Retinopathy/physiopathology , Fluorescein Angiography/methods , Fovea Centralis/pathology , Retinal Vein Occlusion/physiopathology , Retinal Vessels/pathology , Tomography, Optical Coherence/methods , Visual Acuity , Cross-Sectional Studies , Diabetic Retinopathy/diagnosis , Female , Follow-Up Studies , Fundus Oculi , Humans , Male , Middle Aged , Retinal Vein Occlusion/diagnosis , Retrospective Studies , Severity of Illness Index
14.
Article in English | MEDLINE | ID: mdl-27508422

ABSTRACT

PURPOSE: To report a giant retinal pigment epithelium rip in a patient with a bullous retinal and choroidal detachment. METHODS: Case report with widefield imaging, fundus autofluorescence, and optical coherence tomography of the retina. RESULTS: This 62-year-old patient had a history of advanced glaucoma, trabeculectomy, blebitis, and endophthalmitis. He had cataract surgery 6 weeks before presentation. He was found to have a large bullous retinal and choroidal detachment with a large retinal pigment epithelium tear at the limit of the choroidal detachment. After vitrectomy for retinal detachment repair, the tear was observed to extend inferiorly at the margins of the choroidal detachment. CONCLUSION: This case report demonstrates that large retinal pigment epithelium rips can be found associated with large bullous choroidal and retinal detachments. These tears seem similar to tears that have been observed after trabeculectomy.

15.
Clin Ophthalmol ; 9: 2355-71, 2015.
Article in English | MEDLINE | ID: mdl-26719668

ABSTRACT

Choroidal neovascularization (CNV) due to age-related macular degeneration (AMD) is an important cause of visual morbidity globally. Modern treatment strategies for neovascular AMD achieve regression of CNV by suppressing the activity of key growth factors that mediate angiogenesis. Vascular endothelial growth factor (VEGF) has been the major target of neovascular AMD therapy for almost two decades, and there have been several intravitreally-administered agents that have enabled anatomical restitution and improvement in visual function with continual dosing. Aflibercept (EYLEA(®)), initially named VEGF Trap-eye, is the most recent anti-VEGF agent to be granted US Food and Drug Administration approval for the treatment of neovascular AMD. Biologic advantages of aflibercept include its greater binding affinity for VEGF, a longer intravitreal half-life relative to other anti-VEGF agents, and the capacity to antagonize growth factors other than VEGF. This paper provides an up-to-date summary of the molecular mechanisms mediating CNV. The structural, pharmacodynamic, and pharmacokinetic advantages of aflibercept are also reviewed to rationalize the utility of this agent for treating CNV. Results of landmark clinical investigations, including VIEW 1 and 2 trials, and other important studies are then summarized and used to illustrate the efficacy of aflibercept for managing treatment-naïve CNV, recalcitrant CNV, and CNV due to polypoidal choroidal vasculopathy. Safety profile, patient tolerability, and quality of life measures related to aflibercept are also provided. The evidence provided in this paper suggests aflibercept to be a promising agent that can be used to reduce the treatment burden of neovascular AMD.

16.
Rev Sci Instrum ; 81(6): 064101, 2010 Jun.
Article in English | MEDLINE | ID: mdl-20590251

ABSTRACT

Using the technique of modified rapid lifetime determination, pressure-sensitive microspheres, known as PrSBeads, were used to make quantitative oxygen measurements over two-dimensional areas within gaseous flows. Aerosolized PrSBeads in carrier gases of varying oxygen concentrations demonstrated point measurement precisions on the order of 0.1%-1%. A charge-coupled device featuring a double image frame (DIF) feature was used to make spatially resolved pressure measurements within gas phase flows. Errors on the order of 0.5 atm for one standard deviation were demonstrated when 2 x 2 pixel binning (162 x 128 pixel overall resolution) was used, but improved to 0.003-0.005 atm with the use of 32 x 32 pixel binning (10 x 8 pixel overall resolution). Experiments demonstrate the ability to resolve the oxygen concentration differences between a N(2) jet and the surrounding ambient air environment and the ability to measure instantaneous air pressure changes within a square syringe as the plunger is moved in and out. In addition, instantaneous velocity measurements of the airborne PrSBeads in a square syringe were achieved using digital particle image velocimetry at frame rates of 6.4 Hz, thus validating PrSBeads as a tool to simultaneously measure the velocity and pressure within an aerodynamic flow.


Subject(s)
Luminescence , Luminescent Measurements/instrumentation , Luminescent Measurements/methods , Microspheres , Motion , Pressure , Aerosols/chemistry , Air , Air Pressure , Algorithms , Equipment Design , Gases/chemistry , Models, Chemical , Nitrogen , Oxygen/chemistry , Temperature , Time Factors
17.
Chem Commun (Camb) ; (42): 5420-2, 2008 Nov 14.
Article in English | MEDLINE | ID: mdl-18985230

ABSTRACT

Liquid crystal containing composite fibres were produced via coaxial electrospinning, demonstrating that this technique can be used for producing new functional fibres and/or to study the impact of extreme confinement on liquid crystal phases.


Subject(s)
Liquid Crystals/chemistry , Povidone/chemistry , Titanium/chemistry , Electrochemistry , Particle Size , Surface Properties , Temperature
18.
Rev Sci Instrum ; 79(7): 074102, 2008 Jul.
Article in English | MEDLINE | ID: mdl-18681720

ABSTRACT

The response times of pressure sensitive paint (PSP) and pressure sensitive microspheres to passing shockwaves were measured to investigate their ability to accurately determine pressure changes in unsteady flows. The PSPs tested used platinum tetra(pentafluorophenyl)porphine (PtTFPP), platinum octaethylporphine (PtOEP), and a novel set of osmium-based organometallic complexes as pressure sensitive luminophors incorporated into polymer matrices of dimethylsiloxane bisphenol A-polycarbonate block copolymer or polystyrene. Two types of pressure sensitive microspheres were used, the first being PtOEP-doped polystyrene microspheres (PSBeads) and the second being porous silicon dioxide microspheres containing the novel, pressure sensitive osmium complexes. Response times for the platinum-based PSPs ranged from 47.2 to 53.0 micros, while the osmium-based PSPs ranged between 37.6 and 58.9 micros. For the microspheres, 2.5 microm diameter PSBeads showed a response time of 3.15 ms, while the osmium-based silicon dioxide microspheres showed a response time ranging between 13.6 and 18.9 micros.

19.
Nano Lett ; 7(8): 2470-4, 2007 Aug.
Article in English | MEDLINE | ID: mdl-17629350

ABSTRACT

Electrospinning of a polyelectrolyte and vapor deposition polymerization were combined to fabricate nanotubes of oxidatively stabilized poly(acrylonitrile) (PANDelta) with an outer diameter of 100 nm, a wall thickness of 14 nm, and centimeter-scale length. Poly(styrene sulfonate) sodium (PSSNa) nanofibers serves as sacrificial cores while vapor deposition polymerization was used to form smooth PAN sheaths of even thickness. After the PAN sheaths had been oxidatively stabilized, the PSSNa cores were etched away with water to form nanotubes of PANDelta. High-temperature carbonization of these nanotubes at 900 degrees C under Ar flow yielded carbon nanotubes with an outer diameter of 80 nm and wall thickness of 10 nm. Raman spectroscopy confirms that the carbon nanotubes were composed of highly disordered graphene sheets, consistent with the carbonization of PAN under similar conditions. These carbon nanotubes have many promising applications as catalyst supports, gas absorbents, and as encapsulants for controlled release of active compounds.


Subject(s)
Crystallization/methods , Electrochemistry/methods , Electrolytes/chemistry , Nanotechnology/methods , Nanotubes, Carbon/chemistry , Nanotubes, Carbon/ultrastructure , Polymers/chemistry , Gases/chemistry , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Particle Size , Rotation , Surface Properties
20.
Nano Lett ; 6(12): 2868-72, 2006 Dec.
Article in English | MEDLINE | ID: mdl-17163721

ABSTRACT

We have developed a method based on melt coaxial electrospinning for fabricating phase change nanofibers consisting of long-chain hydrocarbon cores and composite sheaths. This method combines melt electrospinning with a coaxial spinneret and allows for nonpolar solids such as paraffins to be electrospun and encapsulated in one step. Shape-stabilized, phase change nanofibers have many potential applications as they are able to absorb, hold, and release large amounts of thermal energy over a certain temperature range by taking advantage of the large heat of fusion of long-chain hydrocarbons. We have focused on compounds with melting points near room temperature (octadecane) and body temperature (eicosane) as these temperature ranges are most valuable in practice. We have produced thermally stable, phase change materials up to 45 wt % octadecane, as measured by differential scanning calorimetry. In addition, the resultant fibers display novel segmented morphologies for the cores due to the rapid solidification of the hydrocarbons driven by evaporative cooling of the carrier solution. Aside from the fabrication of phase change nanofibers, the melt coaxial method is promising for applications related to microencapsulation and controlled release of drugs.

SELECTION OF CITATIONS
SEARCH DETAIL
...