Near-unity quantum yields of biexciton emission from CdSe/CdS nanocrystals measured using single-particle spectroscopy.

Biexciton photoluminescence (PL) quantum yields (Q(2X)) of individual CdSe/CdS core-shell nanocrystal quantum dots with various shell thicknesses are derived from independent PL saturation and two-photon correlation measurements. We observe a near-unity Q(2X) for some nanocrystals with an ultrathick 19-monolayer shell. High Q(2X)'s are, however, not universal and vary widely among nominally identical nanocrystals indicating a significant dependence of Q(2X) upon subtle structural differences. Interestingly, our measurements indicate that high Q(2X)'s are not required to achieve complete suppression of PL intensity fluctuations in individual nanocrystals.

The remarkable influence of M2delta to thienyl pi conjugation in oligothiophenes incorporating MM quadruple bonds.

Oligothiophenes incorporating MM quadruple bonds have been prepared from the reactions between Mo(2)(TiPB)(4) (TiPB = 2,4,6-triisopropyl benzoate) and 3',4'-dihexyl-2,2'-:5',2''-terthiophene-5,5''-dicarboxylic acid. The oligomers of empirical formula Mo(2)(TiPB)(2)(O(2)C(Th)-C(4)(n-hexyl)(2)S-(Th)CO(2)) are soluble in THF and form thin films with spin-coating (Th = thiophene). The reactions between Mo(2)(TiPB)(4) and 2-thienylcarboxylic acid (Th-H), 2,2'-bithiophene-5-carboxylic acid (BTh-H), and (2,2':5',2''-terthiophene)-5-carboxylic acid (TTh-H) yield compounds of formula trans-Mo(2)(TiPB)(2)L(2), where L = Th, BTh, and TTh (the corresponding thienylcarboxylate), and these compounds are considered as models for the aforementioned oligomers. In all cases, the thienyl groups are substituted or coupled at the 2,5 positions. Based on the x-ray analysis, the molecular structure of trans-Mo(2)(TiPB)(2)(BTh)(2) reveals an extended Lpi-M(2)delta-Lpi conjugation. Calculations of the electronic structures on model compounds, in which the TiPB are substituted by formate ligands, reveal that the HOMO is mainly attributed to the M(2)delta orbital, which is stabilized by back-bonding to one of the thienylcarboxylate pi* combinations, and the LUMO is an in-phase combination of the thienylcarboxylate pi* orbitals. The compounds and the oligomers are intensely colored due to M(2)delta-thienyl carboxylate pi* charge transfer transitions that fall in the visible region of the spectrum. For the molybdenum complexes and their oligomers, the photophysical properties have been studied by steady-state absorption spectroscopy and emission spectroscopy, together with time-resolved emission and transient absorption for the determination of relaxation dynamics. Remarkably, THF solutions the molybdenum complexes show room-temperature dual emission, fluorescence and phosphorescence, originating mainly from (1)MLCT and (3)MM(deltadelta*) states, respectively. With increasing number of thienyl rings from 1 to 3, the observed lifetimes of the (1)MLCT state increase from 4 to 12 ps, while the phosphorescence lifetimes are approximately 80 micros. The oligomers show similar photophysical properties as the corresponding monomers in THF but have notably longer-lived triplet states, approximately 200 micros in thin films. These results, when compared with metallated oligothiophenes of the later transition elements, reveal that M(2)delta-thienyl pi conjugation leads to a very small energy gap between the (1)MLCT and (3)MLCT states of <0.6 eV.

Surgical management of optic disc pit associated maculopathy.

PURPOSE: To report the surgical outcome in seven cases of optic disc pit associated maculopathy. METHODS: This was a retrospective case-note analysis of presenting features, pre- and postoperative visual acuities, surgical procedures, complications, and follow-up. The principal treatment in all the cases was pars plana vitrectomy, posterior hyaloid peel, endolaser to the papillomacular bundle temporal to the disc, and internal tamponade with gas or silicone oil. RESULTS: Of the four male and three female patients, two were children. All the patients had posterior hyaloid peeling during the vitrectomy and endolaser. Six patients had intraocular gas tamponade and one had silicone oil. Four patients needed a second surgical procedure to obtain a satisfactory anatomic and visual outcome. Postoperatively, four patients had an improvement of 2 or more Snellen lines. One patient with a history of multiple surgeries developed high intraocular pressure postoperatively and cataract. The mean follow-up period was 9.1 months. CONCLUSIONS: Serous retinopathy associated with optic disc pit responds well to early vitrectomy, endolaser, and internal tamponade. Silicone oil was effective in one refractory case. Cumulative data are required to define the management of this condition.

Nature of linkage between the cationic headgroup and cholesteryl skeleton controls gene transfection efficiency.

Three novel cationic cholesterol derivatives with different modes of linkage between the cationic headgroup and the cholesteryl backbone have been synthesized and used as mixtures with 1, 2-dioleoyl-L-alpha-glycero-3-phosphatidyl ethanolamine (DOPE) for liposome-mediated gene transfection. A pronounced improvement in gene transfer efficiency was observed when the cationic center was appended to the cholesteryl backbone using an ether linkage as opposed to when the linkages were based on either ester or urethane groups. Amphiphiles with ether links such as cholest-5-en-3beta-oxyethane-N,N,N-trimethyl ammonium bromide (2) and cholest-5-en-3beta-oxyethane-N,N-dimethyl-N-2-hydroxyethyl ammonium bromide (3) showed transfection efficiencies considerably greater than commercially available gene transfer reagents. Notably, the transfection ability of 2 with DOPE in the presence of serum was significantly greater than Lipofectamine((R)) and Lipofectin((R)). Interestingly, 3 did not require the helper lipid DOPE for transfection. This suggests that these newly described cholesterol-based amphiphiles should be very promising in liposome-mediated gene transfection. The advantage that the ether linkage possesses would be important in the design of newer, more efficient cholesterol-based delivery reagents.

Cervical intraepithelial neoplasia in Jordan: A ten year retrospective cytoepidemiologic study.

Occurrence of cervical intraepithelial neoplasia (CIN) was studied in 10,659 females attending obstetric and gynecology clinics in Jordan. The frequency rate of intraepithelial neoplasia was 1.1% in 7743 Jordanian females and 2916 non-Jordanian residents of younger age during the period from 1982 to 1991 inclusive. The incidence rate in 2649 Jordanian females, selected because they attended only for routine checkup, was 49 per 100,000. There were 121 CIN cases which were graded into Grade I (21%), II (48%) and III (31%) respectively. Histological grading correlated with cytology in 70% of the cases while in the remaining 30%, cytologic underrating by one grade was noted; evidence against any overdiagnosis of CIN in our series. Study of the human papillomavirus (HPV) was outside the scope of this effort. However, circumcision in male partners and marital status were associated with a lower frequency of CIN. Age at marriage and average duration, parity, breast feeding, the contraceptive pill, socioeconomic status and menstrual disorders showed no relationship to the frequency of CIN in our patients. Any differences in the latter between Jordanian and non-Jordanian females are believed due to cultural factors. Conization in 27 cases proved effective at 30 months' follow-up. Occurrence of CIN in Jordanian females appears substantial although much lower than that seen in high incidence zones, while its incidence in the general female population remains to be determined. This study shows for the first time the value of Papanicolaou (Pap) smears in Jordanian females over 20 years of age with special emphasis on those over 35 years of age attending obstetric and gynecology clinics.

Posterior polar cataract surgery - a posterior segment approach.

PURPOSE: To suggest a surgical approach that would pre-empt uncontrolled posterior capsular rupture and consequent posterior segment complications associated with posterior polar cataract surgery. DESIGN: An interventional case series. METHODS: This was a prospective, interventional study undertaken at a tertiary referral ophthalmic unit. Eleven eyes of eight patients underwent planned pars plana vitrectomy, lensectomy and posterior chamber sulcus fixated intra-ocular lens implantation. Demography, presenting features, pre- and post-operative visual acuities, complications and length of follow-up were recorded. A single surgical technique was performed in all the cases. RESULTS: Five male and three female patients with a mean age of 49.7 years, underwent this procedure. The median-corrected pre-operative visual acuity was 6/12 and the same post-operatively was 6/6. The only major per-operative complication was one case of accidental iridectomy. Post-operatively there were transient choroidal folds in one case, mild posterior segment haemorrhage in another and retinal detachment in one patient. The mean follow-up period was 13 months. CONCLUSIONS: This surgical technique offers a relatively controlled and predictable approach to posterior polar cataract surgery compared to others described in the literature. Although this technique is not without complications, the visual outcome is usually good.

Effectiveness of emergency argon laser retinopexy performed by trainee doctors.

OBJECTIVE: To report the outcomes following treatment of retinal tears with argon laser photocoagulation by trainee doctors as an emergency procedure. METHODS: Retrospective, case note analysis of 100 consecutive patients treated between August 2000 and December 2002 at a tertiary referral hospital. RESULTS: The case notes of 100 consecutive patients (41 male, 59 female) with a mean age of 57.5 years were reviewed. Out of these 90 were symptomatic. The follow-up period ranged from 1 week to 8 months. All patients had argon laser retinopexy in the Emergency department. The on-call Registrar performed the procedure on 94 patients, and Senior House Officers performed the other six. A total of 98 procedures were performed on the slit lamp and two by laser indirect ophthalmoscope. In all, 24 patients needed further treatment with either indirect laser, cryotherapy, or surgery. At the last follow-up, all the patients had anatomically attached retinas. CONCLUSION: A significant proportion of patients (24%) undergoing laser retinopexy in the emergency department needed further treatment. The relative inexperience in using the indirect laser, together with its unavailability in the Emergency department, may be the contributory factors. There seems to be scope for supervised training in using the laser indirect ophthalmoscope for the trainees in the Ophthalmic Emergency department.

Surgical treatment and outcome of patients with giant retinal tears.

OBJECTIVE: To report the management and outcome in retinal detachments associated with giant retinal tears (GRTs). METHODS: Retrospective, case note analysis of patients treated between November 1991 and June 2002 at a tertiary referral hospital. RESULTS: The case notes of 29 patients (24 males, 5 females) with a follow-up ranging from five months to 7 years were reviewed. In all, 25 eyes had retinal detachments with macular involvement and 10 patients had myopia more than 6 D. All patients underwent vitrectomy. A total of 23 patients had heavy liquid and 16 had scleral explants; 28 patients had silicone oil and one had C3F8 tamponade. Intraoperative complications included lens trauma and iatrogenic GRT. Six eyes had recurrent retinal detachment and needed multiple surgical procedures. At the last follow-up, 25 patients had anatomically attached retinas. In all, 18 fellow eyes were treated prophylactically. Three patients had total retinal detachment and marked PVR. The visual acuity improved in 20 eyes. CONCLUSION: GRTs are more common in patients with high myopia. With newer techniques of surgical treatment of GRTs, the anatomical and visual outcomes are more favourable.