Angular momentum generation in nuclear fission

When a heavy atomic nucleus splits (fission), the resulting fragments are observed to emerge spinning¹; this phenomenon has been a mystery in nuclear physics for over 40 years^2,3. The internal generation of typically six or seven units of angular momentum in each fragment is particularly puzzling for systems that start with zero, or almost zero, spin. There are currently no experimental observations that enable decisive discrimination between the many competing theories for the mechanism that generates the angular momentum^4-12. Nevertheless, the consensus is that excitation of collective vibrational modes generates the intrinsic spin before the nucleus splits (pre-scission). Here we show that there is no significant correlation between the spins of the fragment partners, which leads us to conclude that angular momentum in fission is actually generated after the nucleus splits (post-scission). We present comprehensive data showing that the average spin is strongly mass-dependent, varying in saw-tooth distributions. We observe no notable dependence of fragment spin on the mass or charge of the partner nucleus, confirming the uncorrelated post-scission nature of the spin mechanism. To explain these observations, we propose that the collective motion of nucleons in the ruptured neck of the fissioning system generates two independent torques, analogous to the snapping of an elastic band. A parameterization based on occupation of angular momentum states according to statistical theory describes the full range of experimental data well. This insight into the role of spin in nuclear fission is not only important for the fundamental understanding and theoretical description of fission, but also has consequences for the γ-ray heating problem in nuclear reactors^13,14, for the study of the structure of neutron-rich isotopes^15,16, and for the synthesis and stability of super-heavy elements^17,18.

Evaluation of Vela Diagnostics HIV-1 genotyping assay on an automated next generation sequencing platform

BACKGROUND

Antiretroviral drug resistance testing is an integral part of the management of patients infected with HIV. The traditional Sanger sequencing method is capable of detecting drug resistant mutations (DRMs) that make up at least 10-15% of the viral quasispecies population. Newer next generation sequencing technologies have a greater sensitivity for the detection of minority variant DRMs down to around 1% of the population.

OBJECTIVES

Here NGS sequencing on the Vela Diagnostics automated next generation sequencing platform was evaluated and compared to the currently used Sanger sequencing method.

STUDY DESIGN

Sequences from both methods were obtained from a total of 79 patients, with a range of subtypes (CRF01_AE, A1/G, A1/CRF01_AE, A1/CRF02_AG, A1, A, B, C, CRF01_AG, CRF 06_CPX, D, G, B/G, CRF 57_BC/C, G/CRF 02_AG and CRF 14_BG/G) and viral loads (2.43-7 log10 copies/ml).

RESULTS

A high concordance was seen between the two methods for subtyping (96%) and majority variant detection (97.9%). NGS sequencing detected more variants and DRMs than Sanger sequencing. Of the 76 patient samples 86% (n = 66) had identical drug resistance reports. From the ten discrepant reports, nine had extra DRMs detected by NGS sequencing and all discrepancies were seen for NRTI and NNRTI antiviral resistance.

CONCLUSIONS

This study demonstrated a good performance of the NGS method for HIV-1 genotyping compared to the Sanger sequencing method for detection of majority variants, however the reproducibility for the detection of minority variants was sub-optimal. Adoption of an NGS sequencing approach has the potential to improve the clinical management of HIV-infected patients.

Evaluating the aptima HIV-1 quant Dx, HCV quant Dx and HBV quant assays against the Abbott HIV-1, HCV and HBV RealTime assays

BACKGROUND

Viral load measurement is routine for the management of patients infected with HIV, HCV or HBV, using sensitive, quantitative, nucleic acid amplification tests (NAATs). However, platforms are not equivalent in terms of turnaround time, random access capability and operator hands-on time.

OBJECTIVES AND STUDY DESIGN

We compared the performance of the Hologic Panther transcription-mediated amplification based Aptima assays for HIV, HBV and HCV viral load measurement with the corresponding Abbott m2000 RealTime assays. All Aptima assays were run according to the manufacturer's instructions, on archived patient samples for HIV (n = 251 including subtypes 01_AE, A (A1), B, BG recombinant, C CRF02_AG and G), HBV (n = 117 including genotypes A, B, C and D) and HCV (n = 82 including genotypes 1, 2, 3 and 4). Additional testing was performed with WHO international standards and expanded HIV-1 subtype and HCV NIBSC genotype panels.

RESULTS

The Hologic Panther Aptima assays for HIV-1 RNA, HBV DNA and HCV RNA viral load measurements performed equivalently to the Abbott m2000 RealTime assays. The performance of the Aptima assays was also acceptable on the WHO and NIBSC standards and subtype/genotype panels.

CONCLUSIONS

The Aptima Panther platform offers equivalent clinical performance for the viral load measurement of these three viruses, with the added benefits of reduced turnaround time, random access capability and reduced 'hands-on time' for staff, resulting in a potentially superior workflow for diagnostic laboratories.

Convenient and efficient syntheses of N(6)- and N(4)- substituted adenines and cytosines and their 2'-deoxyribosides

Convenient and efficient methods of the synthesis of N(6)- and N(4)-substituted derivatives of adenine and cytosine and their 2'-deoxyribosides were developed. The reactions of either unprotected nucleobases (adenine, cytosine) or unprotected 2'-deoxyribosides with aryl or alkyl aldehydes give corresponding Schiff bases that can be reduced to the target title compounds with high overall yields. In the case of aryl aldehydes the imine derivatives are obtained in the presence of methoxides in methanol and reduced with sodium borohydride. The corresponding reactions with alkyl aldehydes require the use of acetic acid and borane dimethyl sulfide complex instead.

[Differences in dietary habits and food preferences of adults depending on the age]

BACKGROUND

Changes in the structure and functioning of the body occur with age. Also nutrition is continually modified. Eating habits may affect favorably or unfavorably on the process of aging and the functioning of various tissues, organs and the whole body.

OBJECTIVES

The purpose of the study was to evaluate dietary habits and food preferences of patients in different age groups. In the studied groups also body mass index (BMI) and body fat content were analyzed.

MATERIAL AND METHOD

237 people (133 women and 104 men, age 18-79 years) were examined. The participants completed questionnaires of the frequency of food consumption and food preferences. The height, weight, body mass index (BMI), the percentage of body fat (BIA) were also measured. For statistical analysis the assessment of correlation Spearman's rank order and nonparametric ANOVA rank Kruskal-Wallis were used.

RESULTS

With age, the frequency of milk (p < 0,05) and cheese (p < 0,05) consumption decreased whereas consumption of cottage cheese increased (p < 0,05). Increased consumption of offal (p < 0,05), salt (p < 0,05) and coffee (p< 0, 05) was also noted. With age, the respondents preferred animal fats (p < 0.05) and vegetable fats (p < 0.05). The frequency of butter consumption decreased (p < 0.05) and consumption of vegetable fats increased (p < 0,05). The consumption of brown rice (p < 0,05), whole wheat pasta (p < 0,05) and cereals (p < 0,05) was reduced whereas the consumption of groats (p < 0,05) potatos (p < 0,05) and fruits (p < 0,05) increased. The decreased desire (p < 0,05) and frequency of nuts / almonds consumption (p < 0,05) were noted. With age, the BMI and percentage of body fat were increasing (p < 0,05, R = 0,39, p < 0,05, R = 0,31, respectively).

CONCLUSIONS

Taste preferences and dietary habits vary depending on age and may be one of the elements affecting the increase in BMI, body fat content, bone mass loss and increased risk of metabolic disorders. The observed changes in dietary habits can contribute to the development of dyslipidemia, glucose dysmetabolism and arterial hypertension, especially in the presence of overweight and obesity.

[Periventricular haemorrhagic infarction in prematurely born babies]

OBJECTIVES

Periventricular haemorrhagic infarction observed in premature infants is associated with intraventricular haemorrhage (IVH), which leads to obstruction of the terminal veins of periventricular white matter. This lesion has characteristic ultrasonographic evolution. The objectives of this study were to determine the frequency of occurrence of periventricular haemorrhagic infarction in premature infants in intensive care unit and to evaluate the risk factors.

METHODS

A total of 203 premature infants weighing less then 1500 g at birth underwent standardized cranial ultrasound between November 1997 and June 2000.

RESULTS

A total of 156 premature infants with VLBW and ELBW had IVH of various degree and 17 (8,4%) had periventricular haemorrhagic infarction (PHI). 14 babies with PHI died. Among the survivors, 2 exhibit spastic hemiparesis and one had signs of tetraplegia at 6 months of age.

CONCLUSIONS

This study indicates, that PHI occurs more often in neonates, who required a lot of volume expansion due to systemic hypotension. Antenatal glucocorticoid administration has a protective function.

[Ibuprofen--a new application for pharmacological closure of patent ductus arteriosus in preterm infants. Preliminary report]

Patent ductus arteriosus (PDA) remains a frequent problem in premature infants, particularly with very low birth weight. Left-to-right shunting through the ductus may increase the risk of intraventricular hemorrhage, necrotizing enterocolitis, bronchopulmonary dysplasia and death. Indomethacin is the conventional pharmacologic treatment of patent ductus arteriosus (PDA). Although indomethacin is effective in closing PDA, its use may be associated with negative influences on renal, gastrointestinal and cerebral blood flow. More recently Ibuprofen has been tested; it can close the ductus arteriosus, but compared it with indomethacin, it has no negative influence on intestinal haemodynamics. On the basis of relevant literature, ibuprofen and indomethacin have been compared with regard to efficacy for closure of patent ductus arteriosus and side effects.

Regeneration of Cuphea wrightii (Peyr 651) and fertile C.wrightii C. tolucana hybrids from leaf explants

Callus was obtained from leaf explants of Cupea wrightii and Cuphea wrightii x Cuphea tolucana hybrid plants, and the plants were later regenerated. C. tolucana explants were capable of forming callus, but not of regenerating. In order to obtain callus from C. wrightii and the hybrid plants, the addition of BAP to the medium was necessary, whereas in the case of C. tolucana auxin was needed. The regeneration of the plants did not require auxin, and both forms (C. wrightii and the hybrids) regenerated in the same medium. The regeneration yield came to around 12 plants from the callus of one harvest. Some of the callus from the hybrids was subjected to colchicine treatment, which increased the number of fully fertile regenerants from 1% to almost 20%.

Regeneration of Cuphea tolucana Peyr. in in vitro culture

In order to regenerate Cuphea tolucana from hypocotyl, cotyledon and root explants, a solid culture and 8 hormone combinations were used. Only the root explants did not react to any of the media. On most of the media, the other explants formed shoots, roots or callus, or their reaction was more complex. The regeneration probably occurred via direct organogenesis. The regenerants displayed a wide variety of morphological characteristics. However, their offspring did not show any differences from plants, which had not undergone culture.

[Comparison of casein utilization limited by different amino acids]

Experiments of Wistar rats were made to compare the utilization of proteins limited by sulfur-containing amino acids or isoleucine. The score of the limiting amino acid of the proteins under study was identical (0.65). The diets included 2, 5, 10, 15, 20, 25, 30, 40 and 50 g protein per 100 g diet. Depending on the protein content in the diet, the following values of net protein utilization (NPU) were obtained for protein limited by sulfur-containing amino acids: 0.680, 0.647, 0.616, 0.600, 0.562, 0.460, 0.315, 0.240, 0.210. Meanwhile, the values for protein limited by isoleucine were 0.700, 0.697, 0.600, 0.560, 0.524, 0.450, 0.340, 0.260, 0.200. Despite insignificant differences in feed consumption and weight gains in the animals, the above cited values of the NPU did not differ essentially in terms of test protein concentration under comparison. The data obtained indicate that the biological value of proteins limited by sulfur-containing amino acids does not differ from that of proteins limited by isoleucine.