Search PubMed⌕ Search

Biomedical subjects

S Fahy

Publications and source records attributed to S Fahy.

At least 19 recordsLinked to original sources
PubMed2006

First-principles calculation of alloy scattering in Ge(x)Si(1-x).

First-principles electronic structure methods are used to find the rates of intravalley and intervalley n-type carrier scattering due to alloy disorder in Si(1-x)Ge(x) alloys. The required alloy scattering matrix elements are calculated from the energy splitting of nearly degenerate Bloch states which arises when one average host atom is replaced by a Ge or Si atom in supercells containing up to 128 atoms. Scattering parameters for all relevant Delta and L intravalley and intervalley alloy scattering are calculated. Atomic relaxation is found to have a substantial effect on the scattering parameters. f-type intervalley scattering between Delta valleys is found to be comparable to other scattering channels. The n-type carrier mobility, calculated from the scattering rate using the Boltzmann transport equation in the relaxation time approximation, is in excellent agreement with experiments on bulk, unstrained alloys.

Journal Article↗
PubMed2003

Transient strain driven by a dense electron-hole plasma.

We measure transient strain in ultrafast laser-excited Ge by time-resolved x-ray anomalous transmission. The development of the coherent strain pulse is dominated by rapid ambipolar diffusion. This pulse extends considerably longer than the laser penetration depth because the plasma initially propagates faster than the acoustic modes. X-ray diffraction simulations are in agreement with the observed dynamics.

Journal Article↗
PubMed2001

Lithium use in octogenarians.

OBJECTIVES: To assess the tolerability and side-effect profile of lithium use in a group of octogenarians attending a specialized lithium clinic. METHODS: This is a cross-sectional study looking at all patients of eighty years and over attending a lithium clinic. Charts were examined to assess renal function, thyroid function and level of side-effects during their course of lithium treatment in order to assess the tolerability of this medication in octogenarians. RESULTS: Twelve patients of 80 years and over (with an average age of 83.6 years) were taking lithium for an average period of 53.7 months. They had a mean serum level of 0.42 mmol/l. No patient had to discontinue lithium therapy because of side-effects, even though some patients did develop transient abnormalities of renal function. One patient developed diabetes insipidus. One female patient developed hypothyroidism. CONCLUSIONS: Lithium was well tolerated and was administered safely to this cohort of octogenarians. Monitoring of serum lithium levels and kidney and thyroid function should preferably be done in the setting of a specialized lithium clinic.

Aged↗
PubMed2001

Discontinuation of lithium augmentation in an elderly cohort.

OBJECTIVES: To observe the effects of gradual discontinuation of lithium augmentation therapy in a group of patients over the age of 65 years and to measure the rate of relapse and to identify any factors which would predict relapse. METHODS: This was a naturalistic study involving 21 patients who were on lithium augmentation and whose lithium was discontinued for a variety of clinical reasons. In most cases lithium was tapered and discontinued over a period of 2-12 weeks. Demographic and other variables were collected at baseline and compared between those who remained well and those that subsequently relapsed. RESULTS: Eleven patients (52.4%) relapsed following discontinuation of lithium augmentation. Those who relapsed had been on lithium for significantly longer than those who remained well off lithium (p = 0.007). There was a trend towards more hospital admissions in the relapse group (p = 0.062). CONCLUSIONS: When lithium augmentation therapy is discontinued in elderly depressives over half of these patients relapse. A longer duration of prediscontinuation lithium treatment and more hospital admissions appear to be associated with increased risk of relapse.

Aged↗
PubMed1997

Unilateral papilloedema in a 12 year old girl--a surprising diagnosis.

A previously well 12 year old girl presented with diminished visual acuity and haziness of her left eye. Her examination confirmed visual loss in her left eye and significant disc blurring on fundoscopy. Extensive investigations including computerised tomography of the brain and orbit were normal. Her serum angiotensin converting enzyme (ACE) levels were elevated and subsequent Kveim test was positive confirming the diagnosis of ocular sarcoidosis. She did respond to a course of systemic steroids and over the following 3 years her eye signs and symptoms did correlate well with the ACE level. To date she has not had any systemic or respiratory symptoms. Thus sarcoidosis should be considered in the differential diagnosis of ocular pathology of unexplained aetiology.

Child↗