Wavelength scaling of terahertz pulse energies delivered by two-color air plasmas.

We address the long-standing problem of anomalous growth observed in the terahertz (THz) energy yield from air plasmas created by two-color laser pulses, as the fundamental wavelength λ0 is increased. Using two distinct optical parametric amplifiers (OPAs), we report THz energies scaling like λ0α with large exponents 5.6≤α≤14.3, which departs from the growth in λ02 expected from photocurrent theory. By means of comprehensive 3D simulations, we demonstrate that the changes in the laser beam size, pulse duration, and phase-matching conditions in the second-harmonic generation process when tuning the OPA's carrier wavelength can lead to these high scaling powers. The value of the phase angle between the two colors reached at the exit of the doubling crystal turns out to be crucial and even explains non-monotonic behaviors in the measurements.

Helicobacter pylori infection is not associated with rheumatoid arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) is an autoinflammatory disease caused by genetic susceptibility and environmental triggers, which include infectious agents. Helicobacter pylori, a bacterium that frequently colonizes the stomach, is associated with the development of certain autoinflammatory disorders. This study examined a possible association between H. pylori infection and RA. METHOD: This cohort study was performed in the Central Denmark Region. Patients were enrolled from primary healthcare centres after a urea breath test (UBT) for H. pylori and followed for a median of 8 years. Nationwide administrative registries provided information about the patients' diagnoses, country of birth, and gender. Comorbidity was determined using the Charlson Comorbidity Index. We compared the prevalence of RA via odds ratios (ORs) and incidences using Cox regression to calculate the hazard ratios (HRs) by comparing H. pylori-positive and H. pylori-negative individuals and adjusting for confounding variables. RESULTS: A total of 56 000 people diagnosed as H. pylori positive or negative had similar rates of comorbidity. No link was found between H. pylori and RA. There was no difference in RA prevalence until time of UBT [OR = 0.91, 95% confidence interval (CI) 0.70-1.19)] or incidence of new RA cases after UBT (HR = 0.80, 95% CI 0.56-1.13) between H. pylori-positive and -negative subjects. Validation via four other RA definitions provided similar results. CONCLUSION: This study found no association between H. pylori infection and RA. This result does not support the involvement of H. pylori in a gut-joint axis of importance for RA development.

Risk of all-type cancer, hepatocellular carcinoma, non-Hodgkin lymphoma and pancreatic cancer in patients infected with hepatitis B virus.

The increased risk of hepatocellular carcinoma (HCC) among patients infected with hepatitis B virus (HBV) is well established; however, long-term risk estimates are needed. Recently, it has been suggested that HBV is associated with non-Hodgkin lymphoma (NHL) and pancreatic cancer (PC). The aim of this Danish nationwide cohort study was to evaluate the association between HBV infection and all-type cancer, HCC, NHL and PC. A cohort of patients infected with HBV (n = 4345) and an age- and sex-matched population-based comparison cohort of individuals (n = 26,070) without a positive test for HBV were linked to The Danish Cancer Registry to compare the risk of all-type cancer, HCC, NHL and PC among the two groups. The median observation period was 8.0 years. Overall, the incidence rate ratio (IRR) for all-type cancer among HBV-infected patients was 1.1 (95% confidence intervals (CI) 0.9-1.3). The IRR of HCC was 17.4 (CI 5.5-54.5), whereas the IRR of PC and NHL was 0.9 (CI 0.3-2.5) and 1.2 (CI 0.4-3.6), respectively. HBV-infected patients had a 10-year risk of 0.24% (Cl 0.12-0.44) for HCC, whereas the comparison cohort had a 10-year risk of 0.03% (Cl 0.02-0.07) for HCC. The risk of all-type cancer, NHL and PC was not higher in the HBV-infected cohort compared to non-HBV infected. We found a 17-fold higher risk of HCC for HBV-infected individuals.

The impact of urgency of umbilical hernia repair on adverse outcomes in patients with cirrhosis: a population-based cohort study from England.

INTRODUCTION: Umbilical hernia is common in patients with cirrhosis; however, there is a paucity of dedicated studies on postoperative outcomes in this group of patients. This population-based cohort study aimed to determine the outcomes after emergency and elective umbilical hernia repair in patients with cirrhosis. METHODS: Two linked electronic healthcare databases from England were used to identify all patients undergoing umbilical hernia repair between January 2000 and December 2017. Patients were grouped into those with and without cirrhosis and stratified by severity into compensated and decompensated cirrhosis. Length of stay, readmission, 90-day case fatality rate and the odds ratio of 90-day postoperative mortality were defined using logistic regression. RESULTS: In total, 22,163 patients who underwent an umbilical hernia repair were included and 297 (1.34%) had cirrhosis. More patients without cirrhosis had an elective procedure, 86% compared with 51% of those with cirrhosis (P < 0.001). In both the elective and emergency settings, patients with cirrhosis had longer hospital length of stay (elective: 0 vs 1 day, emergency: 2 vs 4 days, P < 0.0001) and higher readmission rates (elective: 4.87% vs 11.33%, emergency:11.39% vs 29.25%, P < 0.0001) than those without cirrhosis. The 90-day case fatality rates were 2% and 0.16% in the elective setting, and 19% and 2.96% in the emergency setting in patients with and without cirrhosis respectively. CONCLUSION: Emergency umbilical hernia repair in patients with cirrhosis is associated with poorer outcomes in terms of length of stay, readmissions and mortality at 90 days.

Hepatitis B prevalence in Denmark - an estimate based on nationwide registers and a national screening programme, as on 31 December 2007.

The prevalence of chronic hepatitis B virus (HBV) infection in Denmark is not clear. The primary aim of this study was to estimate the prevalence of chronic HBV infection in Denmark. The capture­recapture method was used to estimate the total population diagnosed with chronic HBV infection in Denmark using four nationwide registers. The population with undiagnosed chronic HBV infection was estimated by incorporating data from a two-year nationwide HBsAg screening programme in pregnant women. We identified 4,466 individuals with chronic HBV infection in the four registers until the end of 2007, and the capture­recapture estimate of the total population diagnosed with chronic hepatitis B was 7,112 (95% confidence interval (CI): 6,953­10,747). Only 17% of the identified patients attended recommended clinical care according to national guidelines. Including undiagnosed patients, the current population alive with HBV infection was 10,668 (95% CI: 10,224­16,164), corresponding to a prevalence of 0.24% (95% CI: 0.23­0.37%) in the Danish population older than 15 years. The estimated prevalence of chronic HBV infection among adults in Denmark was lower than reported from other northern European countries. Only half of the infected population had been diagnosed, and a minority attended specialised clinical care.

Terahertz field enhancement to the MV/cm regime in a tapered parallel plate waveguide.

We investigate field enhancement properties of a tapered parallel plate waveguide for ultrashort terahertz (THz) pulses. We use two independent methods, air biased coherent detection inside the waveguide and free-space electro-optic sampling, respectively, which enables a calibrated, quantitative measurement of the field strength at the output of the waveguide. Field enhancement factors greater than 20 are demonstrated and record-high field strengths of > 1.4 MV/cm are reached. We find an excellent agreement between the two independent methods of field measurement and a numerical 3D full-vectorial time-domain simulations.

Ultrabroadband terahertz spectroscopy of a liquid crystal.

Liquid crystals (LCs) are becoming increasingly important for applications in the terahertz frequency range. A detailed understanding of the spectroscopic parameters of these materials over a broad frequency range is crucial in order to design customized LC mixtures for improved performance. We present the frequency dependent index of refraction and the absorption coefficients of the nematic liquid crystal 5CB over a frequency range from 0.3 THz to 15 THz using a dispersion-free THz time-domain spectrometer system based on two-color plasma generation and air biased coherent detection (ABCD). We show that the spectra are dominated by multiple strong spectral features mainly at frequencies above 4 THz, originating from intramolecular vibrational modes of the weakly LC molecules.

Optical waveguide mode control by nanoslit-enhanced terahertz field.

In this Letter we propose a scheme providing control over an optical waveguide mode by a terahertz (THz) wave. The scheme is based on an optimization of the overlap between the optical waveguide mode and the THz field, with the THz field strength enhanced by the presence of a metallic nanoslit surrounding the waveguide. We find an optimum balance between the optical mode attenuation and Kerr-induced change in the propagation constant. The criterion for a π/2-cumulative phase shift, for instance for application in a Mach-Zehnder interferometer configuration, requires 10 kV/cm THz field, which in turn is estimated to result in a nonlinear change of the refractive index in the waveguide of 0.001. Our simulations prove that it is quite reasonable to observe the effect experimentally.

Direct observation of sub-100 fs mobile charge generation in a polymer-fullerene film.

The formation of mobile charges in a roll-to-roll processed poly-3-hexylthiophene-fullerene bulk heterojunction film is observed directly by using transient terahertz spectroscopy with sub-100 fs temporal resolution. The transient terahertz ac conductivity reveals that 20% of the incident pump photons are converted into highly delocalized charges within the 40 fs, 3.1 eV pump pulse duration, which then rapidly becomes localized within 120 fs. Approximately 2/3 of these carriers subsequently decay, possibly into an exciton, on a 1 ps time scale.

Unifying interfacial self-assembly and surface freezing.

X-ray investigations reveal that the monolayers formed at the bulk alkanol-sapphire interface are densely packed with the surface-normal molecules hydrogen bound to the sapphire. About 30-35 °C above the bulk, these monolayers both melt reversibly and partially desorb. This system exhibits balanced intermolecular and molecule-substrate interactions which are intermediate between self-assembled and surface-frozen monolayers, each dominated by one interaction. The phase behavior is rationalized within a thermodynamic model comprising interfacial interactions, elasticity, and entropic effects. Separating the substrate from the melt leaves the monolayer structurally intact.

Mortality in HIV-infected injection drug users with active vs cleared hepatitis C virus-infection: a population-based cohort study.

Acute hepatitis C virus (HCV) infection may lead to chronic HCV-infection with detectable HCV RNA or to spontaneous clearance with no HCV RNA, but detectable HCV antibodies. It is unknown whether HCV RNA status is associated with mortality in HIV-infected injection drug users (IDUs). We conducted a nationwide population-based cohort study to examine the impact of HCV RNA status on overall and cause-specific mortality in HIV-infected IDUs. We computed cumulative mortality and used Cox Regression to estimate mortality rate ratios (MRR). We identified 392 HIV-infected patients of whom 284 (72%) had chronic HCV-infection (HCV RNA positive patients) and 108 (28%) had cleared the HCV-infection (HCV RNA negative patients). During 1286 person-years of observation (PYR), 157 persons died (MR = 122/1000 PYR, 95% CI: 104-143). The estimated 5-year probabilities of survival were 0.58 (95% CI: 0.51-0.65) in the chronically HCV-infected and 0.52 (95% CI: 0.40-0.63) in the cleared HCV group. Chronic HCV-infection was not associated with overall mortality: MRR 0.85, 95% CI: 0.59-1.21. In HIV-infected Danish IDUs, chronic HCV-infection is not associated with increased mortality compared to patients who have cleared the infection.

The impact of HIV-1 co-infection on long-term mortality in patients with hepatitis C: a population-based cohort study.

OBJECTIVE: To investigate the impact of HIV co-infection on mortality in patients infected with hepatitis C virus (HCV). METHODS: From a nationwide Danish database of HCV-infected patients, we identified individuals diagnosed with HCV subsequent to an HIV diagnosis. For each co-infected patient, four control HCV patients without HIV were matched on age, gender and year of HCV diagnosis. Data on comorbidity, drug abuse, alcoholism and date of death were extracted from two healthcare databases. We constructed Kaplan-Meier curves and used Cox regression analyses to estimate mortality rate ratios (MRRs), controlling for comorbidity. RESULTS: We identified 483 HCV-HIV co-infected and 1932 HCV mono-infected patients, yielding 2192 and 9894 person-years of observation with 129 and 271 deaths, respectively. The 5-year probability of survival was 0.74 [95% confidence interval (CI) 0.69-0.80] for HCV-HIV co-infected patients and 0.87 (95% CI 0.85-0.89) for HCV mono-infected patients. Co-infection was associated with substantially increased mortality (MRR 2.1, 95% CI 1.7-2.6). However, prior to the first observed decrease in CD4 counts to below 300 cells/muL, HIV infection did not increase mortality in HCV-infected patients (MRR 0.9, 95% CI 0.5-1.50). CONCLUSIONS: HIV infection has a substantial impact on mortality among HCV-infected individuals, mainly because of HIV-induced immunodeficiency.

Hospital admission for non-fatal poisoning with weak analgesics and risk for subsequent suicide: a population study.

BACKGROUND: Poisoning with weak analgesics is a major public health problem because of easy accessibility of the compounds; however, few studies have investigated their influence on subsequent suicide in the context of subjects' psychiatric status and other factors. METHOD: This nested case-control study was based on the entire Danish population including all 21,169 suicide cases and 423,128 matched population controls. Data on hospital admissions for poisoning and confounding factors were retrieved from national medical and administrative registries. Conditional logistic regression was used to compute relative risk. RESULTS: A prior hospital admission for poisoning with weak non-opioid analgesics significantly increased the risk of subsequent suicide [crude incidence rate ratio (IRR) 24.7, 95% confidence interval (CI) 22.1-27.6], and the effect of paracetamol poisoning was substantially stronger than that of poisoning with salicylates or non-steroidal anti-inflammatory drugs (NSAIDs). This association could not be explained by confounding from socio-economic or psychiatric factors. The elevated risk was extremely high during the first week following the overdose (adjusted IRR 738.9, 95% CI 173.9-3139.1), then declined over time but still remained significantly high 3 years later (adjusted IRR 4.2, 95% CI 3.5-5.0). Moreover, a history of weak analgesic poisoning significantly interacted with a person's psychiatric history, increasing the risk for subsequent suicide substantially more for persons with no history of psychiatric hospitalization than did it for those with such a history. CONCLUSIONS: A history of non-fatal poisoning with weak analgesics is a strong predictor for subsequent suicide. These results emphasize the importance of intensive psychiatric care of patients following overdose.

Optical modulation of terahertz pulses in a parallel plate waveguide.

In this work we present a technique for optically modulating a terahertz pulse inside a parallel plate waveguide. A novel semiconductor filled waveguide is formed by coating both sides of a thin, high resistivity silicon slab with a transparent conducting oxide. While the waveguide is intrinsically lossy due to the low conductivity of the oxides, it permits photoexcitation through the plates, generating free carriers within the silicon that modulates the terahertz pulse transmission. We demonstrate this modulation by observing the Drude response of photoexcited carriers within the silicon in a narrow strip inside the waveguide.

A nationwide study of the incidence and 30-day mortality rate of pyogenic liver abscess in Denmark, 1977-2002.

BACKGROUND: Pyogenic liver abscess is a life-threatening disease. Accurate data on incidence and prognosis are important, but scarce. AIM: To examine changes in the incidence and 30-day mortality rate of patients with pyogenic liver abscess in Denmark. METHODS: Using nationwide administrative registers, we identified all patients diagnosed with pyogenic liver abscess in Denmark, 1977-2002, and their dates of death. We computed annual standardized incidence and 30-day mortality rates, and used Poisson regression to adjust gender-specific mortality rates for year-by-year differences in age at diagnosis. RESULTS: We identified 1448 patients with pyogenic liver abscess, of whom 54% were men. The crude incidence rate for the entire study period was 11.8 per 1,000,000 for men and 9.7 per 1,000,000 for women. Between 1977 and 2002, the incidence rate increased from 6 to 18 per 1,000,000 for men and from 8 to 12 per 1,000,000 for women. The cumulative 30-day mortality rate was 15% for men and 23% for women. The adjusted 30-day mortality rate decreased from 40% for men and 50% for women to around 10% for both genders. CONCLUSIONS: In this large nationwide study spanning a 26-year period, we found an increasing incidence rate and a decreasing mortality rate of pyogenic liver abscess. We believe that these changes are primarily explained by more sensitive diagnostic tools.

The association between admission for poisoning with paracetamol or other weak analgesics and subsequent admission for psychiatric disorder: a Danish nationwide case-control study.

BACKGROUND: Many cases of paracetamol poisoning are with suicidal intent, but the association between paracetamol poisoning and subsequent psychiatric disorder is unknown. AIM: To examine the association between poisoning with paracetamol or other weak analgesics and subsequent psychiatric disorder. METHODS: The study was set in a nested case-control design and based on nationwide Danish registers. We identified all patients diagnosed with schizophrenia, affective disorder or eating disorder in 1994-1998 and matched population controls. We estimated the relative risk of these psychiatric disorders after admission for paracetamol or nonparacetamol poisoning, adjusting for income, employment and marital status. RESULTS: We included 12,603 cases with psychiatric disorder, and 1.2% had a diagnosis of poisoning compared with 0.2% of the 252,060 matched population controls. Compared with those with no diagnoses of weak analgesic poisoning, the risk of schizophrenia increased 3.9-fold after paracetamol poisoning, and 2.0-fold after nonparacetamol poisoning. The risk of affective disorder increased 12.2-fold after paracetamol poisoning and 2.6-fold after nonparacetamol poisoning. The risk of eating disorder increased 5.0-fold after paracetamol poisoning, and 2.2-fold after nonparacetamol poisoning. The risk of a diagnosis of psychiatric disorder was very high immediately after poisoning and remained increased for more than 10 years. CONCLUSIONS: Paracetamol poisoning is a strong risk marker for psychiatric disorder, particularly affective disorders.

Far-infrared vibrational modes of DNA components studied by terahertz time-domain spectroscopy.

The far-infrared dielectric function of a wide range of organic molecules is dominated by vibrations involving a substantial fraction of the atoms forming the molecule and motion associated with intermolecular hydrogen bond vibrations. Due to their collective nature such modes are highly sensitive to the intra- and intermolecular structure and thus provide a unique fingerprint of the conformational state of the molecule and effects of its environment. We demonstrate the use of terahertz time-domain spectroscopy (THz-TDS) for recording the far-infrared (0.5-4.0 THz) dielectric function of the four nucleobases and corresponding nucleosides forming the building blocks of deoxyribose nucleic acid (DNA). We observe numerous distinct spectral features with large differences between the molecules in both frequency-dependent absorption coefficient and index of refraction. Assisted by results from density-functional calculations we interpret the origin of the observed resonances as vibrations of hydrogen bonds between the molecules.

Trichophytobezoars in miniature swine.

Miniature swine confined indoors on concrete developed gastric trichophytobezoars that resulted in gradual weight loss and debilitation. The ability to maintain the swine on a chronic research project was threatened by premature deaths associated with the trichophytobezoar formation. The predisposing husbandry practices and history of the development of the trichophytobezoars included confinement for several years and consumption of pelleted feed directly from the concrete floor. Gastrotomy performed on 3 sows and 5 boars avoided the progression of complications leading toward starvation and resulted in clinical improvement.

[Methodological problems of depression research]. / Metodeproblemer i depressionsforskningen.

Controlled clinical trials on the effect of the new antidepressive drugs are encumbered by a number of methodological weaknesses, one of which is lack of placebo control in many studies. The main problem in research into depression is, however, the overlooked issue of how to validate the diagnosis of depression. The agreed diagnostic inclusion criteria in these studies are the diagnostic criteria from the DSM-III or the ICD-10. These disease classifications are in accordance with what has been called the epidemiological disease model. The conclusions of all clinical trials are, however, based on the assumption of a different disease model, the bio-medical disease model. There has truly been a documented effect of these drugs in controlled clinical trials of groups of patients diagnosed with depression, but this conclusion is not stronger than the validity of the diagnosis of depression itself. The categorization of antidepressive drugs as drugs with antidepressive effect has a similar basis even if these drugs were introduced on the basis of a theory of the neurobiology of depression. It is therefore perhaps unclear what has really been documented in these studies. The time has come for a closer inspection of how to use the controlled clinical trial in the field of depression, as well as for a discussion and clarification of what we mean when we use the diagnosis of depression.