Hanbury Brown-Twiss effect with electromagnetic waves.

The classic Hanbury Brown-Twiss experiment is analyzed in the space-frequency domain by taking into account the vectorial nature of the radiation. We show that as in scalar theory, the degree of electromagnetic coherence fully characterizes the fluctuations of the photoelectron currents when a random vector field with Gaussian statistics is incident onto the detectors. Interpretation of this result in terms of the modulations of optical intensity and polarization state in two-beam interference is discussed. We demonstrate that the degree of cross-polarization may generally diverge. We also evaluate the effects of the state of polarization on the correlations of intensity fluctuations in various circumstances.

Cognitive functioning in a population-based sample of young adults with anxiety disorders.

OBJECTIVE: Cognitive functioning in anxiety disorders has received little investigation, particularly among young adults and in non-clinical samples. The present study examined cognitive functioning in a population-based sample of young adults with anxiety disorders in comparison to healthy peers. METHODS: A population-based sample of 21-35-year-olds with a lifetime history of anxiety disorders (n=75) and a random sample of healthy controls (n=71) derived from the same population were compared in terms of performance in neuropsychological tests measuring verbal and visual short-term memory, verbal long-term memory, attention, psychomotor processing speed, and executive functioning. RESULTS: In general, young adults with anxiety disorders did not have major cognitive impairments when compared to healthy peers. When participants with anxiety disorder in remission were excluded, persons with current anxiety disorder scored lower in visual working memory tests. Current psychotropic medication use and low current psychosocial functioning associated with deficits in executive functioning, psychomotor processing speed, and visual short-term memory. CONCLUSION: Lifetime history of anxiety disorders is not associated with cognitive impairment among young adults in the general population. However, among persons with anxiety disorders, current psychotropic medication use and low psychosocial functioning, indicating more severe symptoms, may associate with cognitive impairments.

The effect of psychiatric co-morbidity on cognitive functioning in a population-based sample of depressed young adults.

BACKGROUND: Psychiatric co-morbidity is often inadequately controlled for in studies on cognitive functioning in depression. Our recent study established no major deficits in cognition among young adults with a history of pure unipolar depression. The present study extends our previous work by examining the effects of psychiatric co-morbidity and other disorder characteristics on depression-related cognitive functioning. METHOD: Performance in verbal and visual short-term memory, verbal long-term memory and learning, attention, processing speed, and executive functioning was compared between a population-based sample aged 21-35 years with a lifetime history of unipolar depressive disorders (n=126) and a random sample of healthy controls derived from the same population (n=71). Cognitive functioning was also compared between the subgroups of pure (n=69) and co-morbid (n=57) depression. RESULTS: The subgroups of pure and co-morbid depression did not differ in any of the cognitive measures assessed. Only mildly compromised verbal learning was found among depressed young adults in total, but no other cognitive deficits occurred. Received treatment was associated with more impaired verbal memory and executive functioning, and younger age at first disorder onset with more impaired executive functioning. CONCLUSIONS: Psychiatric co-morbidity may not aggravate cognitive functioning among depressed young adults. Regardless of co-morbidity, treatment seeking is associated with cognitive deficits, suggesting that these deficits relate to more distress.

Mental disorders in young adulthood.

BACKGROUND: The effect of mental disorders may be particularly detrimental in early adulthood, and information on mental disorders and their correlates in this age group is important. METHOD: A questionnaire focusing on mental health was sent to a nationally representative two-stage cluster sample of 1863 Finns aged 19 to 34 years. Based on a mental health screen, all screen-positives and a random sample of screen-negatives were asked to participate in a mental health assessment, consisting of the Structured Clinical Interview for DSM-IV (SCID-I) interview and neuropsychological assessment. We also obtained case-notes from all lifetime mental health treatments. This paper presents prevalences, sociodemographic associations and treatment contacts for current and lifetime mental disorders. RESULTS: Forty percent of these young Finnish adults had at least one lifetime DSM-IV Axis I disorder, and 15% had a current disorder. The most common lifetime disorders were depressive disorders (17.7%) followed by substance abuse or dependence (14.2%) and anxiety disorders (12.6%). Of persons with any lifetime Axis I disorder, 59.2% had more than one disorder. Lower education and unemployment were strongly associated with current and lifetime disorders, particularly involving substance use. Although 58.3% of persons with a current Axis I disorder had received treatment at some point, only 24.2% had current treatment contact. However, 77.1% of persons with a current Axis I disorder who felt in need of treatment for mental health problems had current treatment contact. CONCLUSIONS: Mental disorders in young adulthood are common and often co-morbid, and they may be particularly harmful for education and employment in this age group.

Cognitive functioning in a population-based sample of young adults with a history of non-psychotic unipolar depressive disorders without psychiatric comorbidity.

BACKGROUND: There is evidence for cognitive dysfunction in unipolar depression among middle-aged and elderly patients, but cognitive functioning among depressed young adults has scarcely been systematically investigated. The aims of the present study were to examine cognitive functioning among depressed young adults identified from the general population and to determine whether cognitive deficits vary as a function of different disorder characteristics, such as severity and age at onset. METHODS: Performance in verbal and visual short-term memory, verbal long-term memory and learning, attention, processing speed, and executive functioning was compared between a population-based sample of 21-35-year-olds with a lifetime history of non-psychotic unipolar depressive disorders without psychiatric comorbidity (n=68) and healthy controls derived from the same population (n=70). RESULTS: Depressed young adults were not found to be impaired in any of the assessed cognitive functions, except for some suggestion of mildly compromised verbal learning. Nevertheless, younger age at depression onset was associated with more impaired executive functioning. LIMITATIONS: The results may slightly underestimate of the true association between depression and cognitive impairments in the young adult population due to possible dropout of participants. Additionally, the problem of multiple testing was not entirely corrected. CONCLUSION: The findings from this study indicate that a lifetime history of non-psychotic unipolar depressive disorders among young adults without psychiatric comorbidity may be associated only with minimal cognitive deficits, even when some residual depressive symptoms are prevalent. However, early-onset depression may represent a more severe form of the disorder, associated with more cognitive dysfunction.

Dipole-dipole interaction between molecules mediated by a chain of silver nanoparticles.

We study the dipole-dipole coupling between two fluorescent molecules in the presence of a chain of metallic nanoparticles. We analyze the spectral behavior of the coupling strength and its dependence on the molecular orientation. Our results show that for certain resonant wavelengths the coupling strength between the molecules is greatly enhanced and is strongly polarization sensitive. We also demonstrate how metallic nanoparticles can be utilized in implementing a polarization-sensitive coupler.

Rotational frequency shifts in partially coherent optical fields.

We study the frequency shifts taking place when a random, stationary optical field rotates with respect to an observer. The field is expanded in terms of fully coherent Laguerre-Gaussian basis modes, for which the rotational frequency shifts have been studied previously. We demonstrate the formalism by considering the spectrum of a Gaussian Schell-model field, and show that for a spatially highly incoherent field, significant spectral changes can be expected.

Connection between electric and magnetic coherence in free electromagnetic fields.

We introduce quantitative measures for the description of the electric and magnetic coherence in a stationary, random electromagnetic field at two points, in a volume, and in the Fourier space. These quantities are applied to free electromagnetic fields, and several theorems regarding the relationship between the two types of coherences in such fields are established. Fields which are statistically homogeneous, and those which, in addition, are statistically isotropic are considered separately. Furthermore, the connection between the electric and magnetic coherence is exemplified for some specific statistically homogeneous fields.

Atomic force microscopy study of cellulose surface interaction controlled by cellulose binding domains.

Colloidal probe microscopy has been used to study the interaction between model cellulose surfaces and the role of cellulose binding domain (CBD), peptides specifically binding to cellulose, in interfacial interaction of cellulose surfaces modified with CBDs. The interaction between pure cellulose surfaces in aqueous electrolyte solution is dominated by double layer repulsive forces with the range and magnitude of the net force dependent on electrolyte concentration. AFM imaging reveals agglomeration of CBD adsorbed on cellulose surface. Despite an increase in surface charge owing to CBD binding to cellulose surface, force profiles are less repulsive for interactions involving, at least, one modified surface. Such changes are attributed to irregularity of the topography of protein surface and non-uniform distribution of surface charges on the surface of modified cellulose. Binding double CBD hybrid protein to cellulose surfaces causes adhesive forces at retraction, whereas separation curves obtained with cellulose modified with single CBD show small adhesion only at high ionic strength. This is possibly caused by the formation of the cross-links between cellulose surfaces in the case of double CBD.

Spectral analysis of resonant transmission of light through a single sub-wavelength slit.

We analyze the spectral properties of resonant transmission of light through a sub-wavelength slit in a metal film. We show that the enhanced transmission can be understood in terms of interfering surface-wave-like modes propagating in the slit. We characterize the effect of geometrical and material properties of the slit on the transmission spectrum. Furthermore, we show that the wavelength of the transmission resonance strongly depends on the surrounding medium. This effect may be utilized in sensors, imaging, and the detection of, e.g. biomolecules.

Universality of electromagnetic-field correlations within homogeneous and isotropic sources.

We investigate the structure of second-order correlations in electromagnetic fields produced by statistically stationary, homogeneous, and isotropic current distributions. We show that the coherence properties of such fields within a low-loss or nondissipative medium do not depend on the source characteristics, but are solely determined by the propagation properties, and that the degree of coherence of the field is given by the sinc law. Our analysis reproduces the known results for blackbody fields, but it applies to a wider class of sources, not necessarily in thermal equilibrium. We discuss the physics behind the universal behavior of the correlations by comparing the results with those obtained by an electromagnetic plane-wave model.

Major depressive episode among young adults: CIDI-SF versus SCAN consensus diagnoses.

BACKGROUND: We aimed to evaluate the diagnostic accuracy of a highly structured diagnostic interview in relation to a semi-structured diagnostic procedure. We compared the World Health Organization Composite International Diagnostic Interview Short Form (CIDI-SF) in diagnosing major depressive episode (MDE) to consensus diagnoses based on the SCAN interview (Schedules for Clinical Assessment in Neuropsychiatry). METHOD: Subjects comprised a follow-up sample of 239 20-24-year-old former high-school students who were administered the SCAN and immediately thereafter the CIDI-SF. Concordance was estimated for 12-month MDE, using different cut-points of the CIDI-SF and for any affective disorders. RESULTS: Correspondence between instruments was moderate for MDE (kappa = 0.43, sensitivity 0.71, specificity 0.82), but better for any affective disorder (kappa = 0.60, sensitivity 0.70, specificity 0.90). Most false negatives suffered from their depression as much as those correctly identified by the CIDI-SF. False negativity was mainly due to not endorsing the stem questions of the CIDI-SF. Of the false positives almost half had an affective disorder other than MDE. CONCLUSIONS: The CIDI-SF seems to function best in identifying a broader category of affective disorders. It could be useful in large-scale community surveys where more extensive psychiatric interviews are not feasible.

Degree of polarization for optical near fields.

We investigate an extension to the concept of degree of polarization that applies to arbitrary electromagnetic fields, i.e., fields whose wave fronts are not necessarily planar. The approach makes use of generalized spectral Stokes parameters that appear as coefficients, when the full 3 x 3 spectral coherence matrix is expanded in terms of the Gell-Mann matrices. By defining the degree of polarization in terms of these parameters in a manner analogous to the conventional planar-field case, we are led to a formula that consists of scalar invariants of the spectral coherence matrix only. We show that attractive physical insight is gained by expressing the three-dimensional degree of polarization explicitly with the help of the correlations between the three orthogonal spectral components of the electric field. Furthermore, we discuss the fundamental differences in characterizing the polarization state of a field by employing either the two- or the three-dimensional coherence-matrix formalism. The extension of the concept of the degree of polarization to include electromagnetic fields having structures of arbitrary form is expected to be particularly useful, for example, in near-field optics.

Process technological effects of deletion and amplification of hydrophobins I and II in transformants of Trichoderma reesei.

Transformants of the Trichoderma reeseistrains QM9414 and Rut-C30 were constructed in which the genes for the two major hydrophobin proteins, hydrophobins I (HFBI) and II (HFBII), were deleted or amplified by molecular biological techniques. Growth parameters and foam production of the transformant strains were compared with the corresponding properties of the parent strains by cultivation in laboratory bioreactors under conditions of catabolite repression (glucose medium) or induction of cellulolytic enzymes and other secondary metabolites (cellulose and lactose media). All the transformed strains exhibited vegetative growth properties similar to those of their parent. The Delta hfb2 (but not the Delta hfb1) transformant showed reduced tendency to foam, whereas both strains overproducing hydrophobins foamed extensively, particularly in the case of HFBII. Enzyme production on cellulose medium was unaltered in the Delta hfb2 transformant VTT D-99676, but both the Delta hfb2 and HFBII-overproducing transformants exhibited somewhat decreased enzyme production properties on lactose medium. Production of HFBI by the multi-copy transformant VTT D-98692 was almost 3-fold that of the parent strain QM9414. Overproduction of HFBII by the transformant VTT D-99745, obtained by transformation with three additional copies of the hfb2 gene under the cbh1 promoter, was over 5-fold compared to production by the parent strain Rut-C30. The Delta hfb2transformant VTT D-99676 produced a greatly increased number of spores on lactose medium compared with the parent strain, whereas the HFBII-overproducing transformant VTT D-99745 produced fewer spores.

The hydrophobins HFBI and HFBII from Trichoderma reesei showing efficient interactions with nonionic surfactants in aqueous two-phase systems.

Fungal hydrophobins are a group of surface active, self-assembling proteins. The filamentous fungus Trichoderma reesei produces two (class II) hydrophobins, HFBI and HFBII. We have studied how these water-soluble hydrophobins behave in two-phase systems using a series of nonionic surfactants with different characteristics. It was found that both hydrophobins, but especially HFBI, had a very high affinity for the surfactants. The highest partitioning coefficient, over 2500, was observed for HFBI with C(11)EO(2). Reducing the disulfides in the protein resulted in a complete loss of affinity for the surfactant, which demonstrates that the interaction is dependent on the disulfide-stabilized conformation. The hydrophobins could be efficiently extracted back from the surfactant phase by addition of alcohols such as isobutanol. Effects of the type of surfactant, temperature, pH, and ionic strength were investigated. The use of this method for purifying the proteins from crude fungal culture supernatants is demonstrated and implications of the protein-polymer interaction are discussed.

Overproduction, purification, and characterization of the Trichoderma reesei hydrophobin HFBI.

Many characteristics of fungal hydrophobins, such as an ability to change hydrophobicity of different surfaces, have potential for several applications. The large-scale processes of production and isolation of these proteins susceptible to aggregation and attachment to interfacial surfaces still needs to be studied. We report for the first time on a method for a gram-scale production and purification of a hydrophobin, HFBI of Trichoderma reesei. A high production level of the class II hydrophobin (0.6 g l(-1)) was obtained by constructing a T. reesei HFBI-overproducing strain containing three copies of the hfb1 gene. The strain was cultivated on glucose-containing medium, which induces expression of hfb1. HFBI hydrophobin was purified from the cell walls of the fungus because most of the HFBI was cell-bound (80%). Purification was carried out with a simple three-step method involving extraction of the mycelium with 1% SDS at pH 9.0, followed by KCl precipitation to remove SDS, and hydrophobic interaction chromatography. The yield was 1.8 g HFBI from mycelium (419 g dw), derived from 15 l of culture. HFBI was shown to be rather unstable to N-terminal asparagine deamidation and also, to some extent, to non-specific proteases although its thermostability was excellent.

One-month prevalence of depression and other DSM-IV disorders among young adults.

BACKGROUND: We aimed to provide prevalence data on depression and other current mental disorders, impairment, need of psychiatric care and use of mental health services among young adults. METHODS: Based on a semi-structured clinical interview, current DSM-IV disorders, impairment, need of psychiatric care and use of mental health services were evaluated in a sample of 20-24-year-old young urban adults (N = 245), mean age 21.8, screened from a baseline population of 706. One-month prevalence estimates for disorders were calculated by the double sampling method, using various additional criteria to identify cases. RESULTS: One in four young adults (23.8%) suffered from a current mental disorder, the most prevalent being depressive (10.8%), anxiety (6.9%), substance use (6.2%) and personality disorders (6.0%). Prevalence estimates varied substantially according to the use of additional diagnostic criteria. Impairment (GAF < 61) together with DSM-IV symptom criteria produced an overall disorder prevalence of 10.3%, and 5.5% for depression. Prevalences were higher for females than males, except for alcohol abuse and personality disorders. Current co-morbidity was found in 39% of subjects with any disorder, and in more than half of those with depression. One-third of subjects with a current disorder reported an associated contact with psychiatric services and 16% had an ongoing contact. CONCLUSIONS: Our findings support the use of additional criteria to produce clinically relevant prevalence data. Co-morbidity should receive special attention due to its amplification of both need for psychiatric care and severity of impairment. Finally, our results show disturbed young adults to be severely undertreated.

Correlates of initiation to cannabis use: a 5-year follow-up of 15-19-year-old adolescents.

Initiation to cannabis is often the first step in the use of illicit drugs. We studied the correlates of initiation in a 5-year follow-up study. A total of 21.4% of the subjects reported using cannabis at some time. Of the 139 users, 89.2% had tried cannabis not more than once or a few times. This initiation to cannabis was related to male gender, absence of mother, frequent lack of interest and early age at first sexual intercourse in logistic regression analysis. These factors seem to be useful in predicting initiation to cannabis.

Predictors of alcohol intake and heavy drinking in early adulthood: a 5-year follow-up of 15-19-year-old Finnish adolescents.

Relative contributions of earlier drinking and smoking vs mental health risk factors in predicting alcohol intake and heavy drinking in young adulthood were assessed. Higher average alcohol intake and heavy drinking (13 or more drinks on one occasion) in 1995 were significantly related to male gender and earlier high scores in 1990 of relief smoking, relief drinking, and their interaction. Parental alcohol problems, social group, perceived degree of social support, trait anxiety, number of negative life events, self-esteem, grade-point average, somatic symptoms score, or immature, neurotic, or mature defence style measured in 1990 did not predict alcohol intake or heavy drinking 5 years later. The findings suggest that alcohol intake and heavy drinking in young adulthood can be predicted by earlier self-reports on relief smoking and alcohol intake in adolescence.

Predictors of somatic symptoms: a five year follow up of adolescents.

BACKGROUND: Somatisation is common among adolescents. AIMS: To study factors predicting somatisation later in adulthood. METHODS: Self report questionnaires were administered at baseline examination in 1990 to students (mean age 16.8 years) in schools, and by mail five years later. Results are based on the 615 subjects with no serious disease or injury at baseline. RESULTS: Regression analyses showed that in men the level of somatic symptoms in 1995 was significantly predicted by the respective level in 1990 and by relief smoking. In women, the level of somatic symptoms in 1995 was significantly predicted by the respective level in 1990, self esteem, and the number of negative life events in 1990. After exclusion of cases with a long standing disease in 1995, the multivariate results remained materially similar except that self esteem was no longer significant among women. CONCLUSION: These findings may help in early identification of adolescents with somatisation persisting into early adulthood.