12 results
A Review of Current Strategies in Treatment-Resistant Schizophrenia: Considering Paliperidone Palmitate LAI With and Without Olanzapine as an Alternative to Clozapine
- Raghav Malik, Muhammad Zaidi
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- CNS Spectrums / Volume 28 / Issue 2 / April 2023
- Published online by Cambridge University Press:
- 14 April 2023, p. 257
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Background
Schizophrenia is a debilitating mental illness that affects patient’s function and quality of life. Estimates indicate a lifetime prevalence of 0.48%, causing up to 13.4 million years of life burdened by disability. 30% of these patients are deemed as having treatment-resident schizophrenia (TRS), a subset of which do not respond to clozapine, the medication designated for TRS. Those that do not respond to clozapine are deemed to have clozapine-resistant schizophrenia (CRS), requiring further augmentation or multiple antipsychotics.
Current limitationsClozapine only has limited formulations available (oral [PO] and dissolving [ODT]) and has a substantial side effect burden. Most serious among these side effects includes agranulocytosis, which in some cases can cause severe infections such as septicemia. Regular blood draws monitoring for this are vital to prevent this dangerous consequence, but place further burden on patients, requiring weekly to monthly lab work and visits. Other common and burdensome side effects include tachycardia, hypotension, sialorrhea, weight gain, and metabolic syndrome, to name a few. However, treatment for TRS is still needed, and further alternatives must be explored.
Proposed alternativesAmong studies done on clozapine, few compare second-generation antipsychotics head-to-head, and those that do find similar improvement in overall symptom burden among multiple antipsychotics, especially olanzapine and paliperidone (in particular, paliperidone palmitate). Due in part to the improved receptor profile of these medications (especially 5-HT2A, 6, and 7) compared to clozapine, they can have similar or superior effect in patients with TRS without substantial patient side effect and functional burden. Paliperidone palmitate formulations are developing that can be spaced further and further apart, allowing for minimal impact on patient’s livelihood, while demonstrating similar overall effect with improved side effect profile. However, onset of action is slow, and an effective adjunct strategy may be to initially administer olanzapine for the first 6 months until peak effect is expected from paliperidone palmitate, at which point monotherapy with paliperidone is preferred.
ConclusionsAlternative therapies for patients with TRS may be more functional with fewer side effects, and this work indicates a particularly effective strategy may be to pursue paliperidone palmitate monotherapy long-term while utilizing the unique combination of paliperidone and olanzapine in the short-term (first 6 months) while awaiting peak efficacy.
FundingNo Funding
Ketamine in the Treatment of Delusions: A Review of the Evidence
- Renzo Costa, John Guieb, Ayyub Imtiaz, Muhammad Zaidi
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- Journal:
- CNS Spectrums / Volume 28 / Issue 2 / April 2023
- Published online by Cambridge University Press:
- 14 April 2023, p. 257
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Introduction
Delusions are defined as fixed false beliefs that are not within normal parameters of society, culture, or religion that can be part of psychotic or mood disorders. They can be difficult to treat and, for some inpatient individuals, persistent delusions can make safe discharge impossible. Ketamine is a dissociative agent that has shown promise in treating mood disorders. Despite this, clinicians hesitate to prescribe this when a patient presents with any type of psychotic symptom. There is proof that ketamine is safe to use with psychotic symptoms, and there is growing evidence that it may be a suitable treatment alternative for delusions resistant to other psychopharmacology.
MethodsA literature review using articles from multiple databases was conducted to gather supporting evidence on the use of ketamine in the context of psychosis. Since there has not been a reported conducted study specifically for ketamine and delusions, a look into its use for psychosis was done to find links between the neurobiology of delusions and the mechanism of action of ketamine.
ResultsCurrent literature does not demonstrate that ketamine within a therapeutic setting exacerbates psychotic symptoms in those with depression or bipolar disorder, regardless of the presence of psychotic features, nor does it reveal that predisposed patients experience lasting psychotic effects. Furthermore, although ketamine is often used to model schizophrenia, brain connectivity seen during ketamine-induced delusions is opposite to the connectivity seen in delusions in the context of chronic schizophrenia. Regardless of connectivity patterns, ketamine appears to act upon many of the same mechanisms that underlie delusions. There is evidence delusions are characterized by low belief flexibility, high prediction error, and high aberrant salience. An animal model of stress-induced cognitive dysfunction found that ketamine corrected the cognitive flexibility deficits. Ketamine has been shown to alter prediction error in those suffering from major depressive disorder, resulting in greater optimism bias when patients update maladaptive beliefs post-ketamine administration. In respect to aberrant salience, neural networks affecting this include midbrain dopaminergic neurons and their projections to striatal and frontal cortical regions. Studies have shown this effect was reduced by ketamine-induced plasticity in the orbitofrontal cortex.
ConclusionPsychotic symptoms may not be an absolute contraindication for ketamine treatment. In fact, ketamine could be beneficial in the treatment of various mental illnesses with psychotic features that are not amenable to classical treatment. The dissociative properties may jump-start treatment while waiting for antipsychotics to work. This could significantly reduce hospital stays, especially for patients in long-term facilities.
FundingNo Funding
Factor Associated with HIV/AIDS knowledge among males: Findings from 2017-18 Pakistan Demographic and Health Survey
- Jamal Abdul Nasir, Muhammad Danish Khan, Syed Arif Ahmed Zaidi
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- Journal of Biosocial Science / Volume 55 / Issue 6 / November 2023
- Published online by Cambridge University Press:
- 16 January 2023, pp. 1169-1177
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Acquired immune deficiency syndrome (UNAIDS) has risen as the serious public health problem across the world. Knowledge about HIV/AIDS is the cornerstone for prevention and treatment. Research is needed to explore the attitude and the effect of different demographic, geographic, and socioeconomic and media exposure factors on males knowledge about HIV in Pakistan. In this study, latest secondary data are used from Pakistan Demographic and Health Survey 2017-18. Sample results show that the majority of the respondents (70%) have knowledge about AIDS. Regression Modeling reveals that man’s knowledge about HIV/AIDS is associated with age, place of residence, educational level, wealth index, ethnicity and media exposure factors. Males of age group 35-39, with higher education, belonging to Pukthon ethnicity, having exposure to mass media on a daily basis and belonging to richest wealth quintile has high Knowledge of HIV/AIDS. For example, the regression model predicts that men between the ages of 35 and 39 from Islamabad who live in urban areas, have higher education, are of Pukhtoon ethnicity, are the head of the household, belong to the richest quintile, work in professional occupations, and use media exposure factors on a daily basis would have probability of 97% of having knowledge of HIV/AIDS. But there is still need to focus to increase the men’s knowledge of HIV/AIDS.
Sleep quality and adherence to medical therapy among hemodialysis patients with depression: a cross-sectional study from a developing country
- Syed Muhammad Jawad Zaidi, Mehwish Kaneez, Javeria Awan, Hamza Waqar Bhatti, Muhammad Hamza, Mishal Fatima, Muhammad Zubair Satti
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- Journal:
- BJPsych Open / Volume 7 / Issue S1 / June 2021
- Published online by Cambridge University Press:
- 18 June 2021, p. S43
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Aims
Depression is a fairly common finding among end-stage renal disease (ESRD) patients on hemodialysis and is an independent risk factor for morbidity and mortality. The psychiatric manifestations of the disease may affect their compliance to medications and alter sleep quality that is often overlooked by nephrologists. This translates into poor quality of life and poorer disease prognosis. Thus, Our study aims to assess the prevalence of depression and its association with compliance to medical therapy and sleep quality among ESRD patients on hemodialysis.
MethodIn this cross-sectional study, a total of 288 hemodialysis patients with a confirmed diagnosis of ESRD were evaluated for depression using Patient Health Questionnaire-9 (PHQ-9) scale. Only the patients with moderate to severe depressive symptoms on PHQ-9 were further evaluated for sleep quality and compliance to medications using the Pittsburgh Sleep Quality Index (PSQI) and Drug Attitude Inventory-10 (DAI-10) respectively. The characteristics of ESRD patients with depression were also assessed. Median PHQ-9, DAI-10, and PSQI scores were calculated and the correlation between study variables was assessed using spearman's correlation.
ResultOf the 288 included participants, 188 (65.27%) had depression as evaluated via PHQ-9. Of these 188 patients, 114 were males while 74 were females. A total of 113 (60.01%) of the depressed patients had poor compliance with medication while 137 (72.87%) patients had poor sleep quality. Higher PHQ-9 scores were positively correlated with disease duration, dialysis years, and time between diagnosis and therapy (r = 0.41, 0.39, and 0.43 respectively) and negatively with marital and employment status (r = −0.32 and −0.49 respectively). Spearman's correlation matrix showed that PHQ-9 scores were negatively correlated with DAI-10 but positively correlated with PSQI scores.
ConclusionThe study indicates a high prevalence of depression among ESRD patients on hemodialysis. Poor sleep quality and non-adherence to medications are extremely common among ESRD patients with depression. These psychiatric components must be considered to optimize medical treatment and improve the quality of life in this subset of patients.
Attitudes of medical students towards psychiatry and mental illnesses: a cross-sectional study from Pakistan
- Mishal Fatima, Raja Adnan Ahmed, Muhammad Hamza, Syed Muhammad Jawad Zaidi, Hassan Nadeem, Mehwish Kaneez
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- BJPsych Open / Volume 7 / Issue S1 / June 2021
- Published online by Cambridge University Press:
- 18 June 2021, pp. S303-S304
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Aims
The increasing burden of mental disorders coupled with the social stigmatization in Pakistan is an immense barrier in combating the emerging mental health crisis. The low number of qualified psychiatrists and poor intake in post-graduate psychiatry training programs in the region further complicates the problem. Thus, our study aims to assess the attitudes of Pakistani medical students towards psychiatry. Furthermore, we also aim to evaluate how experience and different levels of exposure to psychiatry among students affect their attitudes towards psychiatry as a career choice.
MethodThis cross-sectional study was conducted via an online survey made on Google Forms. A total of 831 medical students studying across various private and public medical institutions of Pakistan responded to the survey. The questionnaire comprised of demographical details (gender, age, institution, and academic year) exposure to psychiatry, duration of psychiatry rotation, and personal experience with mental illness. The attitudes of medical students towards psychiatry were evaluated using the English version of the 30-item Attitudes Towards Psychiatry (ATP-30) scale. Chi-square test and multiple regression with backward method were used to analyze the data.
ResultThe Cronbach's alpha value of the ATP-30 scale was 0.830. The participants in our study had a mean score of 107.6 ± 12 on ATP-30. Overall, most participants had a positive attitude towards psychiatry. Multiple regression analysis revealed a significant model pertaining to predictors of attitude toward psychiatry (F (df) = 11.28 (830), P < 0.001). However, the predictors included in the model accounted for only 5.8% of the variation in ATP-30 scores. According to it, those students had a more positive attitude toward psychiatry who identified as female, older and having any sort of exposure toward psychiatric specialty, direct involvement in psychiatric patient care, and reporting personal experience of mental illnesses.
ConclusionOur study showed that medical students had a positive attitude towards psychiatry but female medical students, students with previous exposure to psychiatry, and students with longer psychiatry rotations tend to view psychiatry more positively. The generally positive trend towards psychiatry in Pakistan indicates the need to sustain improvements through proactive measures. We recommend longer placements for medical students in mental health settings for at least 4 weeks or longer. Medical schools should also promote research, discussions, and seminars on different psychiatric illnesses in order to enhance awareness among the students.
Exploring the predictive factors for depression among hemodialysis patients: a case-control study
- Syed Muhammad Jawad Zaidi, Mehwish Kaneez, Hamza Waqar Bhatti, Shanzeh Khan, Shafaq Fatima, Muhammad Hamza, Mishal Fatima
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- BJPsych Open / Volume 7 / Issue S1 / June 2021
- Published online by Cambridge University Press:
- 18 June 2021, pp. S43-S44
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Aims
Depression remains an exceedingly ubiquitous entity that significantly depreciates the quality of life and disease prognosis among end-stage renal disease (ESRD) patients. Even though the deleterious effects of depression on ESRD patients are well-established in the literature, the predictive factors that predispose such patients to depression need to be explored. Our study thus aims to gauge these factors and create a predictive model for optimal psychiatric and medical management of such patients.
MethodAll ESRD patients with a disease duration of at least one year underwent a complete psychiatric evaluation based on DSM-V guidelines preceded by a cognitive evaluation by Mini-Mental State Examination (MMSE). A total of 73 patients diagnosed with moderate to severe major depressive disorder were selected as cases. Patients suffering from recurrent psychotic episodes, having a past or family history of psychiatric illness, being already treated for depression, having any substance abuse (current or past), were excluded from the study. Following the similar guidelines, and exclusion criteria, 146 patients (two controls for each case) having no depression were selected as controls. The cases and controls were studied and matched for a myriad of sociodemographic factors. The various risk factors for depression were evaluated using univariate and multivariate binary logistics analysis.
ResultThe significant risk factors for depression among hemodialysis patients were age (OR = 1.79, CI = 0.47–3.81), comorbidities (OR = 2.13, CI = 0.51–3.96), duration of renal disease (OR = 2.54, CI 0.63–4.28), duration of hemodialysis (OR = 2.36, CI = 0.89–4.11), unemployment (OR = 2.33, CI = 0.79–3.88), and being unmarried (OR = 1.93, CI = 0.44–3.53). Prospect of survival, financial instability, social stigmatization, and effect of comorbidities on ESRD were major concerns for the cases that attributed to their depressive symptoms.
ConclusionThe factors that herald the onset of depression among hemodialysis patients include increasing age, presence of comorbidities, unemployment being unmarried, and increasing duration of hemodialysis. These factors will aid the clinicians to identify high-risk patients that require psychiatric consultation. We recommend prompt psychiatric intervention (pharmacologic or non-pharmacologic) and appropriate patient counseling so that the depressive symptoms can be alleviated and dismal disease prognosis can be prevented among such high-risk patients.
162 Post-lithium Delirious Mania in Patients with Bipolar Disorder
- Muhammad Zaidi, Michael Champ, Aquanette Brown, Tzvetelina Dimitrova
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- CNS Spectrums / Volume 25 / Issue 2 / April 2020
- Published online by Cambridge University Press:
- 24 April 2020, pp. 303-304
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Delirious mania is a life-threatening condition, presenting with symptoms of acute delirium and psychotic mania as a complication of medical or psychiatric condition. It is not recognized as a diagnosis in DSM-V and is under recognized in clinical practice. It was first described by Calmeil (Calmeil, 1832). In 1849 Luther Bell described 40 cases with an associated 75% mortality rate. More recently, Jacobowski et al (2013) compiled a comprehensive review of clinical characteristics, diagnostic work up, and treatment recommendations for delirious mania. In addition to acute onset, clinical course is frequently worsened by psychosis and catatonia. Delirium leads to disequilibrium of neurotransmitters, particularly depletion of acetylcholine and elevation of dopamine.
Lithium has been used for the treatment of mania for many decades. Suppes et al performed a meta-analysis of 14 studies including 257 patients with Bipolar I disorder and concluded that patients relapsed 28 times more when stopping lithium compared to those who continued this medication. Baldessarini et al (1999) completed analysis of 227 patients with Bipolar I and II disorders, dividing the sample into “abrupt” (1-14 days) and “gradual” (15-30 days) discontinuation groups and concluded that the frequency of relapse following “abrupt” cessation was four times higher compared to following “gradual” cessation. In a study of 450 bipolar patients, Baldessarini et al (2003) reviewed the long-term treatment of lithium as monotherapy (86 % of the study’s population) in the context of lithium maintenance population morbidity. Greater pretreatment morbidity lead to larger relative reduction in morbidity as a result of treatment with lithium. A subgroup of bipolar patients with “abrupt” discontinuation became refractory when re-challenged with lithium.
Describing three clinical cases of delirious mania following conclusions can be derived:
• Patients with bipolar disorder and comorbid chronic kidney injury currently or formerly receiving long-term therapy with lithium are at increased risk for delirious mania.
• Abrupt lithium discontinuation in patients with bipolar disorder and comorbid chronic medical conditions (especially chronic kidney disease) increases risk for mania refractory to conventional treatment with medications.
• In such patients, definitive treatment is ECT.
188 Challenges in Differentiating Between Obsession and Delusion in Schizophrenic Patients: A Case Report
- Po Yu Yen, Muhammad Zaidi, Syed Naqvi
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- CNS Spectrums / Volume 25 / Issue 2 / April 2020
- Published online by Cambridge University Press:
- 24 April 2020, pp. 318-319
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Schizophrenia is a serious, chronic mental illness that manifests a variety of symptoms: hallucinations, delusion of grandiose, disorganized behaviors, and neurocognitive decline after each episode. Among the patients with schizophrenia, obsessive- compulsive symptoms (OCS) or obsessive- compulsive disorder (OCD) are two relatively common comorbidities (25% and 12.5%, respectively). The appearance of these comorbidities complicates patient management: selecting the suitable pharmacological treatment may be challenging as delusion and obsession have similar presentation in this population. We would like to present a case which we suggest that differentiation between obsession and delusion will result in a positive impact on disease management.
Patient was a middle- aged male with history of Schizophrenia and status post skin grafting. He presented with delusions, auditory hallucinations and disorganized behavior. During his hospitalization, he spent much portion of a day slapping or hitting his wound. He would not follow staffs’ recommendations regarding wound care as he believed that his behavior would lead to diminishing his pain from skin grafting and shorten the recovery time. He was treated with psychotropic medications, anti-depressants aided with medication for pain. Despite adequate pain management, appropriate dosage of anti-depressants and psychotherapy his self- injurious behavior persisted throughout the course of his hospitalization.
In this report, we presented the challenges in managing compulsive behavior in a patient with Schizophrenia. To date, OCD and OCS are diagnosed based on clinical presentations, which results in difficulty in patient management especially when the illness is complicated by Schizophrenia. Patient was accessed with Yale- Brown Obsessive- Compulsive Scale on multiple occasions which the results indicated that he had subclinical OCD. However, the validity of the test is questionable as it is a test for severity of OCD; If his compulsive behavior was due to delusion rather than obsession, YBOCS should not be applied since it is limited to the patients with OCD.
We propose that there is a necessity of developing a diagnostic intervention that may aid the differentiation between delusion and obsession in Schizophrenic patients. Genetic testing, for example, may be one of the potential diagnostic interventions to utilize clinically: A recent study, “Serotonin system genes and obsessive- compulsive trait dimensions in a population- based, pediatric sample: a genetic association study” by Sinopoli et al, has demonstrated a possible correlation between obsessive- compulsive spectrum disorders and serotonin gene variants. Although genetic testing of OCD is at its early stages and many aspects are yet to be discovered, it is optimistic to believe that potential benefits of the genetic test is tremendous as it will provide physicians a clearer picture in designing a treatment plan for this patient population.
59 “Lithium Damaged My Spine” Might not Be a Delusion After All
- Muhammad Zaidi, Anurag Prabhu, Jose Perez Martell, Sakshi Dhir
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- Journal:
- CNS Spectrums / Volume 24 / Issue 1 / February 2019
- Published online by Cambridge University Press:
- 12 March 2019, pp. 206-207
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Background
Lithium remains to be the drug of choice for treating BPAD for the past few decades. There is extensive literature showing the effectiveness of Lithium when used as a mood stabilizing agent in bipolar spectrum disorders. However significant number of articles show that a third of the patients who receive lithium for their symptomology not only do not show any response but also may show deterioration of their clinical symptoms. (However, research shows that Lithium may negatively affect a third of the patients depending on various factors). The side effect profile of Lithium and especially its neurotoxic effects were discussed in depth in literature over the last decade. Although Lithium remains first choice as maintenance treatment for bipolar affective disorder, about half of all individuals may stop their treatment at some point, despite its proven benefits concerning the prevention of severe affective episodes and suicide.
MethodsThe authors performed a systematic literature review to recognize the significance of negative effects of Lithium in a minority of patient population and also comment on the factors influencing patient compliance. We ran a literature search on Pubmed using the following terms: “Lithium” AND (“schizoaffective disorder [MeSH terms]” OR “Bipolar Affective disorder [MeSH terms]” ). Our inclusion criteria were studies which have observed effects of Lithium in schizoaffective patient population or bipolar affective patient population. Studies with other concurrent diagnoses were excluded.
Case presentationWe discuss a fifty nine year old male with a history of multiple admissions to a forensic hospital care setting. He initially endorsed a diagnosis of Psychotic disorder NOS which was later changed to schizoaffective disorder during his subsequent admissions. He presented with affective psychotic features where his mood was labile shifting from melancholic to euphoric and a concurrent history of auditory verbal hallucinations. He displayed paranoid non-bizarre persecutory delusions and also alleged that one of his doctors had hated him and put him on Lithium as a form of punishment. He claims that Lithium, as a result, has significantly affected him negatively and also damaged his nerves. This led the authors to explore the significance of use of Lithiumin people with schizoaffective disorders and also bipolar affective disorders. We also discuss the disease course in the patient and his clinical response to use of various psychotropic medications.
ConclusionsThe case exemplifies the negative effects of Lithium when used as a mood stabilizer in patient population that is susceptible to its adverse effects due to various factors.
58 Case Report: Clinical Challenges in the Diagnoses and Management of Delirious Mania in a US Veteran with a Mental Health History of Bipolar Disorder
- Muhammad Zaidi, Kurt Brown, Aquanette Brown, Dominique Neptune, Vicenzio-Holder Perkins
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- Journal:
- CNS Spectrums / Volume 24 / Issue 1 / February 2019
- Published online by Cambridge University Press:
- 12 March 2019, pp. 205-206
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A 46 year old Caucasian male veteran with a mental health history of Bipolar Disorder was admitted to the inpatient psychiatric unit following an episode of mania. He was re-started on his outpatient medication regimen for mood stabilization with Quetiapine, Lamotrigine, and Clonazepam. He improved initially, however, on hospital Day 3, the veteran was noted to have acute worsening of manic and psychotic symptoms including, decreased need for sleep, excess energy and responding to internal stimuli. Additionally, he developed symptoms which were atypical for mania, including unprovoked agitation, depersonalization, difficulty sustaining attention, and visual hallucinations. These mental status changes were associated with, excessive motor movement, walking with bizarre postures, squatting, laying taut on the ground, and standing still for several minutes in uncomfortable positions. At this time, Seroquel was switched with Olanzapine for management of mania and psychosis. On physical exam, his vital signs were notable for tachycardia and fever, his extremities were noted to have a normal range of motion; he also experienced loss of bowel continence. The treatment team initiated a medical work up for delirium which revealed no infectious, neurological, or metabolic cause. Of note, there was concern for benzodiazepine withdrawal; however, adequate management did not relieve the symptoms. The veteran was transferred to medicine and neurology was consulted to assist with medical workup. His neuroleptic and benzodiazepine medications were discontinued at that time, except for Lamotrigine. The veteran was then transferred back to psychiatry after medical stabilization, Lamotrigine was discontinued at that time. He was started on Haloperidol, Benztropine and restarted on Clonazepam. At this time, veteran experienced improvement on his mental status exam, with resolution of mania, psychosis, and delirium. However, after two days of treatment, he developed acute rigidity in his extremities. Intramuscular Benztropine and Lorazepam improved his rigidity. Haloperidol was discontinued because of side effects and the veteran was managed with Risperidone and Ativan. He continued to show improvement in his mental status examination and was discharged on a medication regimen of Risperidone, Clonazepam, and Benztropine. The veteran experienced signs and symptoms which were atypical in nature for Bipolar Mania, such as fever, movement disorder, and delirium. This presentation is consistent with a rare medical condition, Delirious Mania for which limited research is available. Delirious mania meets the criteria for mania and delirium with out an underlying medical disorder. Delirious mania is a potentially life threatening but under-recognized neuropsychiatric syndrome. Early recognition and aggressive treatment can significantly reduce morbidity and mortality.
Ga1-xGdxN-Based Spin Polarized Light Emitting Diode
- Muhammad Jamil, Tahir Zaidi, Andrew Melton, Tianming Xu, Ian T. Ferguson
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1290 / 2011
- Published online by Cambridge University Press:
- 21 March 2011, mrsf10-1290-i02-05
- Print publication:
- 2011
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In this work, a room temperature spin-polarized LED based on ferromagnetic Ga1-xGdxN is reported. The device was grown by metalorganic chemical vapor deposition (MOCVD) and is the first report of a spin-LED based on Ga1-xGdxN. Electroluminescence from this device had a degree of polarization of 14.6% at 5000 Gauss and retained a degree of polarization of 9.3% after removal of the applied magnetic field. Ga1-xGdxN thin films were grown on 2 μm GaN templates and were co-doped with Si and Mg to achieve n-type and p-type materials. Co-doping of the Ga1-xGdxN films with Si produced conductive n-type material, while co-doping with Mg produced compensated p-type material. Both Si and Mg co-doped films exhibited room temperature ferromagnetism, measured by vibrating sample magnetometry.
NH3 Doping in MOCVD Growth of ZnO Thin Films
- Tahir Zaidi, Muhammad Jamil, Andrew Melton, Nola Li, William E. Fenwick, Ian T. Ferguson
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1109 / 2008
- Published online by Cambridge University Press:
- 01 February 2011, 1109-B06-01
- Print publication:
- 2008
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In this paper effects of NH3 doping on ZnO thin films grown by metal organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates using diethyl zinc (DEZn) and O2 precursors and N2 as the carrier gas have been studied. NH3 flow rates were varied from 0.1% to 4% in the growth runs. All the runs were done at 500°C at 10 Torr pressure.
The XRD measurements show a single ZnO (002) peak. Raman data for the samples confirms presence of ZnO:N modes at 275cm−1, 510cm−1 and 575 cm−1 and 645cm−1. The PL results for Zn rich films show weak broad peaks centered at 480nm and 650nm with no ZnO band edge emission, while oxygen rich films show weak ZnO band edge emission and a strong broad orange peak centered at 650nm. Hall effect measurements indicate that all of the as-grown films are highly resistive. Some are weakly p-type with carrier concentration of 4.24 × 1014 cm−3 and mobility of 16.55 cm2/Vs. Annealing in N2 ambient for 60 minutes at 800°C enhances the PL band edge emission and converts all the films to highly conducting n-type, with carrier concentration on the order of 8 × 1018 cm−3, mobility on the order of 12 cm2/Vs and resistivity of 0.063 Ω-cm.