Optical reflection and transmission properties of exfoliated graphite from a graphene monolayer to several hundred graphene layers.

The optical reflection contrast and optical transmission contrast of graphitic films on glass ranging in thickness from a monolayer to the limit of bulk graphite have been experimentally measured. For samples with more than 10 graphene layers where optical contrast quantization becomes difficult to observe, atomic force microscopy was used to measure the sample thickness. The visible optical reflection and transmission of thin graphitic films is found to depend strongly on the real component of the optical conductance per graphene layer, and comparatively weakly on the imaginary component of optical conductance. This observation in part explains the significant variation in the refractive index of graphene and graphite reported in the literature to date. Spectroscopic measurements reveal a strong dispersion in the optical conductance of even a 10 layer film, consistent with an imaginary conductance arising from virtual transitions at the band edges of the pi and sigma bands at the M and Gamma points, respectively.

Epidemiology of liver cirrhosis morbidity and mortality in Iceland.

BACKGROUND: The mortality from liver cirrhosis in Iceland is the lowest in the Western world. OBJECTIVE: To study the epidemiology of liver cirrhosis mortality and morbidity in Iceland and to obtain a reliable separation between alcoholic cirrhosis (AC) and non-alcoholic cirrhosis (NAC) by using multiple data sources. METHODS: The study included the whole population of Iceland. Mortality was studied through death certificate data for the period 1951-90 and morbidity (clinical incidence) through hospital, autopsy and biopsy records for the period 1971-90. RESULTS: The average mortality for AC in age group 20 years and older was 8.6 and for NAC 19.2 per 10(6)/year and the average clinical incidence was 22.1 per 10(6)/year for AC and 25.9 per 10(6)/year for NAC. In the morbidity study 44% of cases were due to AC. In the mortality study 24% of cases were due to AC but the data suggested an underreporting of AC for males at a rate of 30%. There was a significant decrease in AC mortality with time but no change in NAC. Average alcohol consumption of inhabitants aged over 15 years increased from 2.1 to 4.9 litres per year (130%) during the period 1951-90. CONCLUSION: The incidence of cirrhosis in Iceland is very low for both AC and NAC, accounting for only 0.2% of total deaths. The reasons are unknown. The low incidence of AC in Iceland is probably partly due to low alcohol consumption. The decreasing incidence of AC despite 130% increase in alcohol consumption is thought to be due to intensive treatment of alcoholism. A low prevalence of hepatitis B and C probably contributes to the low incidence of NAC.

[Epidemiology of liver cirrhosis morbitity and mortality in Iceland.].

BACKGROUND: The mortality from liver cirrhosis in Iceland is the lowest in the Western world. OBJECTIVE: To study the epidemiology of liver cirrhosis mortality and morbitity in Iceland and to obtain a reliable separation between alcoholic cirrhosis (AC) and non alcoholic cirrhosis (NAC) by using multiple data sources. METHODS: The study included the whole population of Iceland. Mortality was studied through death certificate data for the period 1951-1990 and morbidity (clinical incidence) through hospital, autopsy and biopsy records for the period 1971-1990. RESULTS: 1) The average mortality for AC in age group 20 years and older was 8.6 and for NAC 19.2 per 106 per year and the average clinical incidence was 22.1 for AC and 25.9 for NAC. 2) In the morbitity study 44% were due to AC. In the mortality study 24% were due to AC but the data suggested an underreporting of AC for males at a rate of 30%. 3) There was a significant decrease in AC mortality with time but no change in NAC. 4) Alcohol consumption per inhabitant over 15 years increased from 2.1 to 4.9 litre (130%) during the period 1951-1990. CONCLUSION: The incidence of cirrhosis in Iceland is very low for both AC and NAC accounting for only 0.2% of total deaths. The reasons are unknown. The low incidence of AC in Iceland is probably partly due to a low population alcohol consumption. The decreasing incidence of AC despite 130% increase in alcohol consumption is thought to be due to intensive treatment of alcoholism. A low prevalence of hepatitis B and C probably contributes to the low incidence of NAC.