Polarization-resolved spectroscopy imaging of grain boundaries and optical excitations in crystalline organic thin films

Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to submicron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. Here we report on the results of combined linear dichroism (LD)/ polarization-resolved photoluminescence (PL) scanning microscopy experiments that simultaneously probe the excitonic radiative recombination and the molecular ordering in solution-processed metal-free phthalocyanine crystalline thin films with macroscopic grain sizes. LD/PL images reveal the relative orientation of the singlet exciton transition dipoles at the grain boundaries and the presence of a localized electronic state that acts like a barrier for exciton diffusion across the grain boundary. We also show how this energy barrier can be entirely eliminated through the optimization of deposition parameters that results in films with large grain sizes and small-angle boundaries. These studies open an avenue for exploring the influence of long-range order on exciton diffusion and carrier transport.

In-depth understanding of organic crystalline semiconductor thin films is critical for the development of many electronic and photonic devices. Here, the authors use combined linear dichroism and polarization-resolved photoluminescence scanning microscopy to unveil the nature of excited states in such systems.

Prevalence of herpesvirus DNA in MS patients and healthy blood donors

OBJECTIVES

The aim of this study is to determine the DNA prevalence of different members of Herpesviridae in multiple sclerosis (MS) patients and to describe the possible effect of beta-interferon treatment on such prevalence.

MATERIAL AND METHODS

With a nested polymerase chain reaction (PCR) assay we have studied the DNA of the peripheral blood mononuclear cells (PBMCs) of 204 whole blood samples, [102 from patients with relapsing-remitting MS (RRMS), of which 62 were treated with beta-interferon, and 102 from healthy blood donors].

RESULTS

We only found a statistically significant difference for human herpesvirus type 6 (HHV-6) DNA prevalence (P < 0.0001): HHV-6 is 2.26 times more frequent in MS patients than in healthy donors. There was no difference in the HHV-6 prevalence between beta-interferon treated and untreated patients.

CONCLUSION

1. Among the herpesviruses, HHV-6 was the only one showing altered prevalence. This either indicates that HHV-6 is involved in the pathogenesis of MS, or it simply indicates that MS influences latency or reactivation of HHV-6 without any direct involvement of HHV-6 in the disease process of MS. 2. Treatment with beta-interferon does not make a difference on the DNA prevalence of the herpesviruses studied in our MS patients.

[Detection of viral genomes of the Herpesviridae family in multiple sclerosis patients by means of the polymerase chain reaction (PCR)]

BACKGROUND

The multiple sclerosis seems to be the junction between genetics alteration and an unknown environmental factor, that they would originate an autoimmune alteration, that they would be the reason of the inflammation and demyelinization responsible of the disease. Our objective has been the determination of this possible environmental factor and to reach it, we have studied the appearance of Herpesviridae family viruses.

MATERIALS AND METHODS

204 blood samples were studied: 102 from relapsing-remitting multiple sclerosis patients (43 were undergoing beta-interferon treatment), and 102 from blood donors with the same age and sex than multiple sclerosis patients. From this samples, we extracted the DNA of peripheral blood mononuclear cells (PBMCs), and we analyzed by polymerase chain reaction (PCR) to detect the appearance of herpes simplex virus, varicella zoster virus, Epstein-Barr virus, cytomegalovirus, human herpesvirus 6 (HHV-6), human herpesvirus 7 and human herpesvirus 8.

RESULTS

a) we only found significative difference (p = 0.0001) in HHV-6: 21.5% donors positive samples (22/102), opposite to 49.02% of positivity in mulytiple sclerosis patients (50/102); b) we didn't found significative differences in none of other viruses studied, between patients treated with beta-interferon and non-treated ones.

CONCLUSIONS

Our results suggest us that HHV-6 can play an important role in the multiple sclerosis development. The beta-interferon treatment doesn't affect to DNA prevalence of none of studied viruses.

[Cytomegalovirus: comparative study of diagnostic techniques]

BACKGROUND

The aim of this study was to undertake a comparative study of a series of diagnostic techniques of active infection by cytomegalovirus (CMV) in blood (isolation of CMV by shell vial, detection of specific anti-CMV IgG and IgM, antigenemia-detection of pp65 antigen by staining with peroxidase- and two variants of qualitative polymerase chain reaction [PCR]-conventional PCR or in one step and nested PCR-for detection of viral DNA).

METHODS

Fifty kidney transplant patients were followed for the first 6 post transplant months. All except 6 were seropositive for CMV prior to transplantation and only one seronegative patient had a seronegative donor.

RESULTS

A total of 750 blood samples were analyzed, 8 of which were positive by shell vial, 91 by specific IgM detection, 115 by antigenemia, 225 for conventional PCR and 440 for nested PCR. No positive sample was detected throughout follow up by any of the techniques used in only 4 patients (one being the seronegative receptor with a seronegative donor).

CONCLUSIONS

Antigenemia was found to be the fastest, cheapest and simplest method of diagnosing CMV, presenting the advantage of providing quantitative results which allow the establishment of a relationship with the appearance of symptomatic infections. With the two variants used qualitative PCR was observed to be the earliest and most sensitive technique, while being the most difficult and the most expensive, with the disadvantage that its great sensitivity limits its clinical usefulness.