Ultrafast Picometer-Resolved Molecular Structure Imaging by Laser-Induced High-Order Harmonics.

Real-time visualization of molecular transformations is a captivating yet challenging frontier of ultrafast optical science and physical chemistry. While ultrafast x-ray and electron diffraction methods can achieve the needed subangstrom spatial resolution, their temporal resolution is still limited to hundreds of femtoseconds, much longer than the few femtoseconds required to probe real-time molecular dynamics. Here, we show that high-order harmonics generated by intense femtosecond lasers can be used to image molecules with few-ten-attosecond temporal resolution and few-picometer spatial resolution. This is achieved by exploiting the sensitive dependence of molecular recombination dipole moment to the geometry of the molecule at the time of harmonic emission. In a proof-of-principle experiment, we have applied this high-harmonic structure imaging (HHSI) method to monitor the structural rearrangement in NH_{3}, ND_{3}, and N_{2} from one to a few femtoseconds after the molecule is ionized by an intense laser. Our findings establish HHSI as an effective approach to resolve molecular dynamics with unprecedented spatiotemporal resolution, which can be extended to trace photochemical reactions in the future.

Replication study of SNP associations for colorectal cancer in Hong Kong Chinese.

BACKGROUND: Recent genome-wide association studies of colorectal cancer (CRC) have identified common single-nucleotide polymorphisms (SNPs) mapping to 10 independent loci that confer modest increased risk. These studies have been conducted in European populations and it is unclear whether these observations generalise to populations with different ethnicities and rates of CRC. METHODS: An association study was performed on 892 CRC cases and 890 controls recruited from the Hong Kong Chinese population, genotyping 32 SNPs, which were either associated with CRC in previous studies or are in close proximity to previously reported risk SNPs. RESULTS: Twelve of the SNPs showed evidence of an association. The strongest associations were provided by rs10795668 on 10p14, rs4779584 on 15q14 and rs12953717 on 18q21.2. There was significant linear association between CRC risk and the number of independent risk variants possessed by an individual (P=2.29 × 10(-5)). CONCLUSION: These results indicate that some previously reported SNP associations also impact on CRC risk in the Chinese population. Possible reasons for failure of replication for some loci include inadequate study power, differences in allele frequency, linkage disequilibrium structure or effect size between populations. Our results suggest that many associations for CRC are likely to generalise across populations.

Splenic laceration after endoscopic retrograde cholangiopancreatography.

Endoscopic retrograde cholangiopancreatography has been part of clinical practice for over 35 years. The procedure itself carries risks. Most complications associated with the procedure have been described in the literature. Splenic injury is an extremely rare complication after endoscopic retrograde cholangiopancreatography and only nine such cases have been reported to our knowledge since 1988. We report on a patient who presented with abdominal pain and was found to have abnormal liver function and a dilated pancreatic duct. An endoscopic retrograde cholangiopancreatography was performed and a splenic laceration was noted subsequently. As this operation is an increasingly important diagnostic and therapeutic modality for pancreatico-biliary disease, clinicians must be aware of this complication in order to make an early diagnosis and begin appropriate management.

Audit of laparoscopic cholecystectomy in a single center.

A continuous audit is required to ensure laparoscopic cholecystectomy (LC) is performed safely in the surgical community in general. A retrospective review of all LC done in a single center was performed. A total of 1,244 LC were attempted. The conversion rate was 12.4%, the complication rate 3.5%, and the bile duct injury rate 0.4%. Forty percent of bile duct injury occurred after conversion. A decreasing trend of complication rate was seen in the early part of the series, then the rate steadied at about 2.5-3%. A higher threshold of conversion may not increase the bile duct injury rate. However, good laparoscopic technique and adequate experience are prerequisites to safe LC.

The investigation and management of thyroid nodules--a retrospective review of 183 cases.

The management of the patient with a thyroid nodule remains a clinical challenge because of its risk of malignancy. This is a retrospective audit of 183 patients undergoing thyroidectomy for thyroid nodules at the Queen Elizabeth Hospital, Hong Kong, in 1994. The history, physical examination and investigations done were charted and analysed against the final histopathology of the specimens. Age, sex, symptom duration and nodularity were not associated with malignancy statistically, whereas a nodule hard in consistency was shown to be associated with malignancy (P < 0.05). The sensitivity and specificity of ultrasonography, radionuclide scan and fine-needle aspiration cytology (FNAC) were 71% and 57%, 50% and 43%, and 93% and 60%, respectively. Hence, history and physical examination are unreliable for detecting malignant thyroid nodules and FNAC is mandatory. FNAC is superior to ultrasonography or radionuclide scan for evaluating thyroid nodules and should be used as the initial investigation.

Family needs and burdens of mentally ill offenders.

A growing number of research projects have been devoted to the study of needs, burdens and intervention programmes of families of psychiatric patients due to the emphasis on deinstitutionalization and community integration. Although it is noted that burdens for families when looking after a patient with a criminal history are even heavier and more complicated, studies on identifying family needs and burdens for mentally ill offenders have been very limited. This paper reviews literature on family burdens and studies on family needs for psychiatric patients with a forensic history. Methodological problems of available studies are discussed. In addition, a theoretical model that can be used as a conceptual guide for the study of burdens of families of mentally ill offenders is postulated. Directions for further research are discussed.

Phacoemulsification and intraocular lens implantation following pars plana vitrectomy: a prospective study.

AIMS: To examine the intraoperative characteristics of phacoemulsification in eyes that had undergone pars plana vitrectomy and to determine complication rates and visual outcomes. METHODS: A prospective study of 45 consecutive cataract operations on vitrectomised eyes performed over a 9-month period by a single surgeon. Data were collected on preoperative characteristics, intraoperative observations and complications, postoperative complications, and visual acuities. RESULTS: Zonular laxity with abnormal deepening of the anterior chamber and mydriasis was noted in six eyes that had undergone extensive vitreous removal for the treatment of retinal detachment or proliferative diabetic retinopathy, but not in eyes that had had limited 'core vitrectomy' such as for macular hole or epiretinal membrane. In two eyes, the initial deepening of the anterior chamber was accompanied by paradoxical shallowing with miosis (the 'infusion deviation syndrome'). Sight-threatening complications were rare. Snellen visual acuity improved in 84.6% of eyes previously treated for 'macular hole, 85.7% of eyes treated for 'macula-on' retinal detachment, 66.7% of eyes treated for 'macula-off' retinal detachment, and 57.1% of eyes treated for diabetic retinopathy. CONCLUSIONS: Surgeons need to be aware of additional challenges arising from zonular instability in eyes that have had extensive vitreous removal. A lower infusion bottle height may guard against sudden changes in anterior chamber depth. The use of a corneal tunnel avoids difficulties associated with an unusually deep anterior chamber. Visual acuity is less likely to improve in patients previously treated for diabetic retinopathy or for macula-off retinal detachment.

Simple rectovaginal fistulas.

In regard to the causes of simple rectovaginal fistulas (RVF) we examined the methods of diagnosis and the efficacy and outcome of surgical procedures. The study included all of our patients diagnosed with simple RVF between December 1988 and July 1998 (n = 19). Medical charts of these patients were reviewed regarding diagnostic investigations, operative procedure, outcome, and follow-up. The most common cause was obstetric trauma (n = 15, 79%) followed by infection (n = 4, 21%). Eight patients (42%) had undergone anal surgery prior to the development of RVF; two of these had undergone more than one procedure. Endoanal ultrasound was performed in 15 patients and identified the fistula in 11 (73%). A concomitant sphincter injury was visualized in 9 of 15 patients (60%). The most common initial operation performed was an endoanal advancement flap in 12 patients (63%). This operation was performed in combination with a sphincteroplasty in 4 patients, while 3 had sphincteroplasty alone. The mean hospital stay was 3 days (range 1-5). Postoperative morbidity was noted in 5 patients (26%) of and consisted of recurrent fistula and passage of gas per vagina. Surgery was successful in complete resolution of symptoms in 14 cases (74%). Two of the three recurrences were successfully repaired with a repeat endoanal advancement flap, and one is awaiting repair. The mean follow-up for the entire group was 35.8 months (range 6-84). Endoanal advancement flap should be the initial treatment of choice for simple, low rectovaginal fistulas. The procedure can also be employed with expectations of success even after a failed primary repair and should be combined with sphincteroplasty if a coexistent anteriorly based anal sphincter defect is noted either by clinical examination or endoanal ultrasonography.