Room-temperature spontaneous superradiance from single diamond nanocrystals.

Superradiance (SR) is a cooperative phenomenon which occurs when an ensemble of quantum emitters couples collectively to a mode of the electromagnetic field as a single, massive dipole that radiates photons at an enhanced rate. Previous studies on solid-state systems either reported SR from sizeable crystals with at least one spatial dimension much larger than the wavelength of the light and/or only close to liquid-helium temperatures. Here, we report the observation of room-temperature superradiance from single, highly luminescent diamond nanocrystals with spatial dimensions much smaller than the wavelength of light, and each containing a large number (~ 103) of embedded nitrogen-vacancy (NV) centres. The results pave the way towards a systematic study of SR in a well-controlled, solid-state quantum system at room temperature.

Effects of dietary folate on the development and progression of mammary tumors in rats.

Epidemiologic studies have suggested that dietary intake and blood levels of folate may be inversely related to the risk of breast cancer. However, epidemiologic evidence has not been consistent nor has it provided unequivocal support for this purported inverse relationship. Recent evidence has also raised a concern that folate supplementation may promote carcinogenesis if provided after neoplastic foci are established in the target organ. This study investigated the effect of dietary folate deficiency and supplementation on the development and progression of mammary tumors in the N-methyl-N-nitrosourea (MNU) rat model. Weanling, female Sprague-Dawley rats were fed diets containing 0, 2 (control) or 8 mg folic acid/kg diet during the initiation or the promotion phase of MNU-induced mammary tumorigenesis. At necropsy, all macroscopic mammary tumors were identified and histologically confirmed. Dietary folate deficiency and supplementation provided during the initiation phase did not significantly modulate the development of mammary tumors. In contrast, dietary folate deficiency provided during the promotion phase significantly inhibited the rate of appearance, incidence, mean volume and weight of adenocarcinomas compared with the control and supplemental diets. Folate supplementation provided during the promotion phase did not significantly modulate mammary tumorigenesis compared with the control group. These data indicate that moderate folate deficiency inhibits, whereas dietary folate supplementation at four times the basal dietary requirement does not promote, the progression of MNU-induced mammary neoplastic foci in this rat model. However, the limitations associated with the route and dose of MNU administration preclude a definitive conclusion concerning the effect of folate status on the initiation of MNU-induced mammary tumorigenesis.

Effects of dietary folate on ulcerative colitis-associated colorectal carcinogenesis in the interleukin 2- and beta(2)-microglobulin-deficient mice.

Folate supplementation may reduce the risk of colorectal dysplasia and cancer in subjects with chronic ulcerative colitis (UC). The interleukin (IL) 2- and beta(2)-microglobulin (beta(2)m)-deficient (IL-2(null) x beta(2)m(null)) mice spontaneously develop colon cancer in the setting of chronic UC. This study investigated the effects of dietary folate on the development of UC-associated colon cancer in the IL-2(null) x beta(2)m(null) mice. Weaning IL-2(null) x beta(2)m(null) mice were randomized to receive 0 (deficient; n = 40), 2 (basal requirement; control; n = 46), or 8 (supplemented; n = 36) mg folate/kg diet for 32 weeks. At necropsy, all macroscopic colonic tumors were identified and histologically classified as dysplasia or adenocarcinoma. The incidence of high-grade lesions (high-grade dysplasia/carcinoma in situ and invasive adenocarcinoma) in the folate-supplemented group was 46% lower than that in the control group (35.3% versus 65.1%, P = 0.009). The incidence of high-grade lesions in the folate-deficient group was also 49% lower than that in the control group (33.3% versus 65.1%, P = 0.007). The higher mortality rate in the folate-deficient group compared with the other two groups (25% versus 6.5% and 5.6%, P < 0.02) partially accounted for the low incidence of high-grade lesions in this group. These data indicate that dietary folate supplementation at 4x the basal dietary requirement significantly suppresses UC-associated colorectal carcinogenesis in the IL-2(null) x beta(2)m(null) mice. These data also suggest that folate deficiency may inhibit colorectal carcinogenesis in chronic UC. However, the high mortality observed in the folate-deficient group precludes a definitive conclusion concerning the effect of folate deficiency on UC-associated colorectal carcinogenesis in this model.

Dietary folate deficiency suppresses N-methyl-N-nitrosourea-induced mammary tumorigenesis in rats.

Epidemiologic studies have suggested that dietary folate intake is inversely related to breast cancer risk. However, epidemiologic evidence has not been consistent nor has it provided unequivocal support for this purported inverse relationship. This study investigated the effect of dietary folate on N-methyl-N-nitrosourea (MNU)-induced mammary tumorigenesis in rats. Weanling, female Sprague-Dawley rats were fed diets containing either 0 (deficient; n = 22), 2 (basal dietary requirement, control; n = 20) or 8 mg (supplemented; n = 20) folate/kg diet for 30 weeks. At 50 days of age, rats received an i.p. injection of MNU (50 mg/kg body wt). At necropsy, all macroscopic mammary tumors were identified and examined microscopically. The effect of dietary folate on genomic DNA methylation in mammary tumorigenesis was determined by the in vitro methyl acceptance assay. The incidence of mammary adenoma and adenocarcinoma in the folate-deficient group was lower than that of the control and folate-supplemented groups (55 versus 90 and 75%, respectively, P = 0.043). Kaplan-Meier analyses also demonstrated a similar trend in the rates of appearance of either adenoma or adenocarcinoma (P = 0.06). In contrast, folate supplementation did not significantly modulate mammary tumorigenesis compared with the control group. Although mammary tumors were significantly hypomethylated compared with non-neoplastic mammary tissues in each dietary group (P < 0.03), folate status did not significantly affect the extent of DNA methylation. The data suggest that dietary folate deficiency of a moderate degree suppresses, whereas folate supplementation at four times the basal dietary requirement does not significantly modulate, mammary tumorigenesis in this model. The role of folate in mammary tumorigenesis needs to be clarified for safe and effective prevention of breast cancer.

What happens to patients who leave hospital against medical advice?

BACKGROUND: Patients who leave hospital against medical advice (AMA) may be at risk of adverse health outcomes and readmission. In this study we examined rates of readmission and predictors of readmission among patients leaving hospital AMA. METHODS: We prospectively studied 97 consecutive patients who left the general medicine service of an urban teaching hospital AMA. Each patient was matched according to age, sex and primary diagnosis with a control patient who was discharged routinely. Readmission rates were examined using Kaplan-Meier analysis. Regression models were used to test the hypothesis that readmissions among patients discharged AMA followed a biphasic curve. RESULTS: Patients who left AMA were much more likely than the control patients to be readmitted within 15 days (21% v. 3%, p < 0.001). Readmissions occurred at an accelerated pace during the first 15 days, followed by a 75-day period during which readmissions occurred at a rate comparable to that among the control patients. Among the patients who left AMA, being male and having a history of alcohol abuse were significant predictors of readmission within 15 days; however, these characteristics were common among the patients who left AMA. In the Cox proportional hazard models, leaving AMA was the only significant predictor of readmission (adjusted hazard ratio 2.5, 95% confidence interval 1.4-4.4). INTERPRETATION: The significantly increased risk of readmission among general medicine patients who leave hospital AMA is concentrated in the first 2 weeks after discharge. However, it is difficult to identify which patients will likely be readmitted.

The relationship between housing conditions and health status of rooming house residents in Toronto.

BACKGROUND: Rooming houses are an important source of housing for low-income Canadians. Little information is available on the relationship between housing conditions and health status in this vulnerable population. METHODS: Interviews were conducted with a representative sample of 295 residents in 171 rooming houses in Toronto. Health status was assessed using the SF-36. The physical attractiveness of each rooming house was rated using the Multiphasic Environmental Assessment Procedure. Associations between the health status of residents and the physical attractiveness and organizational characteristics of rooming houses were examined. RESULTS: Rooming house residents aged 35 years and older had significantly poorer health status than their counterparts in the Canadian general population. Eight of the ten dimensions of individual health status assessed by the SF-36 were significantly correlated with the physical attractiveness of the rooming house in which the individual lived. However, there was no significant association between residents' health status and the rooming house's non-profit status, provision of meals, or the presence of an on-site landlord. CONCLUSIONS: Rooming house residents suffer from a high prevalence of ill health. Residents reporting worst health are concentrated in rooming houses in the poorest physical condition. This relationship may be mediated by selection processes that place the sickest individuals in the lowest-quality rooming houses, and/or by a direct effect of adverse housing conditions on health status. Further research is needed to elucidate these processes and to improve the health of this vulnerable population.