Health behaviors and problems in Polish homeless men.

Introduction: Homelessness is considered to be a global problem, independent of the material situation of a given country and occurring in most societies around the world. Aim of the study: Assessment of the preferred health behaviors of homeless people. Materials and methods: The study covered 153 men who are homeless and 312 men who are not homeless. The original questionnaire of homeless, and validated the Satisfaction with Life Scale (SWLS), the Health Behavior Inventory (HBI), the General Self-Efficacy Scale (GSES) and the Multidimensional Health Locus of Control (MHLC) Scale were used. The research covered fully completed questionnaires from 153 homeless men staying in Bialystok and Gdansk homelss centers. Results: On average, the homeless men assessed their health at 6.0 ± 2.7 points, and the non-homeless at 7.8 ± 2.2 points (p < 0.001). Significant differences were found between people experiencing a homelessness crisis and the control group in selected aspects concerning the everyday life hygiene of the respondents, health self-assessment, declarations of visits to a specialist and carrying out check-ups, level of satisfaction with life, coping with difficult situations, preferred pro-health behaviors and dimensions of health control. In the used scales, SWLS, HBI, GES, and MHCL, the majority of homeless men obtained average scores. They were rather dissatisfied with their lives, with a low level of effectiveness in coping with difficult situations and obstacles, a low level of health behaviors, and in the scope of health, control increasing the impact of chance. Conclusion: The level of the presented health behaviors showed statistically significant diversification with all dimensions of the health locus of control, and its internal dimension with age, homelessness phase, the respondents' criminal history, being under constant medical care, and self-assessment of health.

Effect of various factors on energy drinks consumption, and their connection with alcohol consumption.

Energy drinks (EDs) have become widely popular among adolescents and young adults. Excessive consumption of EDs can lead to ED abuse and alcohol abuse. Therefore, this study has aimed to analyse the consumption of EDs in a group of patients suffering from alcohol dependence and among young adults, considering such issues as the amounts consumed, underlying reasons and threats arising from excessive consumption of ED and their mixing with alcohol (AmED). The study included 201 men (101 patients treated due to alcohol dependence and 100 young adults/students). Each research participant responded to questions in a survey designed by the researchers (socio-demographic data, clinical data, including consumption of ED, AmED and alcohol), the MAST and SADD. The participants also had their arterial blood pressure measured. EDs were consumed by 92% of the patients and 52% of young adults. A statistically significant dependence was confirmed between consumption of ED and tobacco smoking (p < 0.001), as well as the place of residence (p = 0.044). For 22% of the patients, ED consumption had an effect on alcohol consumption, where 7% admitted to feeling an increased urge to drink alcohol, and 15% said ED consumption decreased it. A statistically significant relationship (p < 0.001) was also shown between ED consumption and the consumption of EDs mixed with alcohol (AmED). This study may implicate that widespread consumption of EDs predisposes to the consumption of alcohol mixed with ED or separate.

The Lack of Influence of Homozygous Long Allele of the 5-HTTLPR Gene on the Severity of Alcohol Craving During 6 Weeks of Rehab Hospitalisation in Comparison to Not Homozygous and Homozygous Short Alleles - Preliminary Report.

Purpose: The aim of this study was to assess changes in the severity of alcohol craving according to allelic variants of the 5-HTTLPR gene polymorphism during hospitalisation and their association with selected clinical variables in alcohol-dependent patients. Patients and Methods: The study is exploratory. Participants were investigated at the 2nd and 6th week of alcohol-dependence therapy in the addiction treatment unit. Recruitment was conducted among alcohol-dependent patients from several Polish drug treatment centres. The total sample size was 130 persons (12 females and 118 males). Study subjects' mean age was 43.0 years. Patients were investigated twice by using the Penn Alcohol Craving Scale (PACS) and Beck Depression Inventory (BDI), and once by using Short Alcohol Dependence Data Questionnaire (SADD) and taking a swab for genetic testing. The polymorphism of the gene encoding the serotonin transporter 5-HTTLPR (SLC6A4) was determined from isolated DNA and its homozygous variants of short/short or long/long alleles and heterozygous short/long alleles were analysed. Results: At 6th week of the follow-up, there was a decrease in the severity of alcohol craving in half of subjects with the short/short allele (p = 0.033) and in one-fifth of subjects with the long/short allele (p = 0.002) of the 5-HTTLPR gene. In subjects with long/long allele of the 5-HTTLPR gene, there was no change in the severity of alcohol craving between 2nd and 6th weeks of the study (p = 0.242). Conclusion: There was no statistical influence of the homozygous long allele of the 5-HTTLPR gene on severity of alcohol craving during 6 weeks of rehab hospitalisation in comparison to not homozygous and homozygous short alleles. The s-allele was associated with decrease of alcohol craving. It may point on the potential need for differentiated rehabilitation methods depending on the genetic diversity of addicted patients and its role in the severity of alcohol craving.

Confusion of Alcohol Craving With Food Hunger in Alcohol-Dependent Individuals Entering In-Patient Drug Treatment.

AIM: To identify the distinguishing characteristics of alcohol dependent patients who confuse alcohol cravings with pre-meal hunger. METHODS: Data were collected at interview on sociodemographic status, clinical status and anthropometry in 179 patients (163 men and 16 women) undergoing in-patient treatment for alcohol dependence. RESULTS: A comparison of the patient subgroups studied showed that patients who did not confuse, and those who did confuse, alcohol craving with pre-meal hunger differed significantly in terms of alcohol craving scale scores (9 vs. 4 points). Patients confusing alcohol cravings with pre-meal hunger were more likely to recognize that experiencing severe pre-meal hunger can cause relapse (67.9 vs. 22.8%) and that not being able to distinguish between the sensations under study also increases the risk of breaking abstinence (75.0% vs. 50.4%). This was independent of severity of dependence and intensity of recent alcohol consumption. CONCLUSIONS: Alcohol-dependent persons who confuse alcohol craving with pre-meal hunger differ from those who do not confuse these hunger pangs in terms of feeling stronger alcohol craving and more frequent occurrence of symptoms accompanying the feeling of alcohol craving during pre-meal hunger. At the start of treatment for alcohol withdrawal, alcohol-dependent individuals who report confusing alcohol cravings with pre-meal hunger are less confident of maintaining abstinence. This is relevant to treatment. The role of possible confounders (depressive symptoms, cognitive and educational deficiency) could not be elucidated definitively.

Initial Study on COMT and DRD2 Gene Polymorphisms as Well as the Influence of Temperament and Character Trait on the Severity of Alcohol Craving in Alcohol-Dependent Patients.

The main aim of this work was to determine the impact of COMT and DRD2 gene polymorphisms together with temperament and character traits on alcohol craving severity alcohol-dependent persons. The sample comprised of 89 men and 16 women (aged 38±7). For the sake of psychological assessment various analytic methods have been applied like the Short Alcohol Dependence Data Questionnaire (SADD), Penn Alcohol Craving Scale (PACS) or Temperament and Character Inventory (TCI) test. The SNP polymorphism of the analyzed genes was determined by Real Time PCR test. The results showed, that the COMT polymorphismmay have an indirected relationship with the intensity and changes in alcohol craving during abstinence. The DRD2 receptor gene polymorphisms are related with the intensity of alcohol craving. It seems that the character traits like "self-targeting", including "self-acceptance", are more closely related to the severity of alcohol craving and polymorphic changes in the DRD2 receptor than temperamental traits. Although this is a pilot study the obtained results appeared to be promising and clearly indicate the link betweengene polymorphisms alcohol craving and its severity.

Validation of the Polish version of the Penn Alcohol Craving Scale (PACS). / Walidacja polskiej wersji Skali Glodu Alkoholu Penn (Penn Alcohol Craving Scale ­ PACS).

OBJECTIVES: The conducted studies were aimed at making a Polish adaptation of the Penn Alcohol Craving Scale (PACS) by B. Flannery and co-workers. The Scale is a self-assessment method, it comprises 5 statements, and is designed to assess alcohol craving experienced by a patient in a week prior to the examination. METHODS: 550 patients with diagnosed alcohol dependence syndrome were examined, and the final analysis included results of 510 persons. The examined group consisted of 396 men and 114 women. The study was made in the 3rd week of their alcohol treatment. There were used: the PENN Craving Scale, the Alcohol Dependence Development Scale (SRUA) (the part in which craving is dealt with), a clinical interview with specially prepared questions about alcohol craving experienced last month and last week, and the Yale-Brown Obsessive Compulsive Intense Drinking Scale. RESULTS: The Polish version of the Penn Scale is characterised by very good psychometric properties - it is a reliable and valid tool. The exploratory and confirmatory factor analyses have proved the existence of one factor. The internal consistency, assessed on the basis of Cronbach's alpha, equalled 0.89. The method displays statistically significant (majority p < 0.0010) relationships with levels of craving experienced last year, last month, and last week before the examination, and also with total score on the Yale-Brown Scale. CONCLUSIONS: The effects of the conducted adaptation works on the Penn Scale speak for recommending the method for scientific research and use in therapeutic practice.

Resilience as a predicator of mental health of incarcerated women. / Preznosc jako predyktor zdrowia psychicznego kobiet odbywajacych kare pozbawienia wolnosci.

OBJECTIVES: Serving a prison sentence is an experience that bears the hallmarks of a trauma. Scientific findings on how people handle traumatic The aim of the following research was to analyze the way in which psychological resilience differentiates mental states of incarcerated women and to identify the predicator of mental well-being in this group.experiences show that there are numerous personal and social resources that allow for better adaptation. One of the concepts used to describe the process reflecting relatively good adaptation is psychological resilience. METHODS: The study included women incarcerated in the External Department of Czersk Penitentiary for juvenile female offenders who serve a prison sentence for the first time and penitentiary recidivists. The following scales were used in the research: the Resilience Measurement Scale - RMS-25 and the HADS-M scale, which allows to conduct a test for symptoms of depression. RESULTS: The results revealed crucial statistical correlations between the results of the resilience scale and results of the HADS-M. It was also found that the predicators of anxiety and depression in the study group are the level of personal coping skills and tolerance of negative emotions (RMS-25). Additionally, a crucial factor in predicting the state of anxiety is the number of years of imprisonment. The conducted regression analysis also showed that the level of personal coping skills and tolerance of negative emotions (RMS-25) as well as openness to new experiences and sense of humor (RMS-25) are essential predicators of the level of aggression. CONCLUSIONS: The concept of psychological resilience is significant in analyzing the differences in mental health of incarcerated women and may help to create conditions that are conducive to reducing negative effects of prisoners staying in conditions of institutional constraint.

Suicidal thoughts in persons treated for alcohol dependence: The role of selected demographic and clinical factors.

Greater knowledge is needed of potential predictive factors for suicide in cases of alcohol addiction. Therefore, the aim of the study was to identify the socio-demographic variables and clinical factors associated with alcohol dependence which may have an influence on the occurrence of suicidal thoughts in alcohol-dependent patients. A group of 510 patients (396 male and 114 female) diagnosed with alcohol dependence syndrome were interviewed during the third week of therapy according to the Beck Depression Inventory (BDI), the Penn Alcohol Craving Scale (PACS) and the Short Alcohol Dependence Data Questionnaire (SADD). Socio-demographic data was also collected. The results of a binary logistic regression with suicidal thoughts as a dependent variable show that 63 out of the 510 participants (12% of the sample) reported the presence of suicidal thoughts. Alcohol dependence and alcohol craving appear to increase the likelihood of suicidal thoughts, and participants presenting psychiatric disorders were twice as likely to demonstrate suicidal ideation as those who did not. Alcohol dependence, alcohol craving and psychiatric comorbidity may be regarded as risk factors for suicidal ideation in the studied sample, with the only protective factor being living in a relationship.

Blood glucose and lipid concentrations after overload are not associated with the risk of alcohol relapse.

AIMS: There is evidence for the functioning of feedback between alcohol consumption and fat (positive) and carbohydrate (negative) intake. We tried to verify the hypothesis that blood glucose and lipid concentration in a fasting state and after loading may affect the risk of relapse in alcohol-dependent male patients during withdrawal therapy. METHODS: Blood glucose, total cholesterol (TC) and triglycerides (TG) were determined at the beginning of the study, and again after 4 weeks and 6 months of observation in 54 alcohol-dependent male patients treated against drinking relapse. Glucose concentration was checked after fasting and 2h after loading with a 75 g water solution of glucose, and blood lipids were determined on an empty stomach and 5h after butter loading (0.5 g of butter per kilogram of body mass). RESULTS: Patients who relapsed compared to subjects who remained abstinent during the 6-month observation did not differ significantly in relation to blood glucose, TC or TG blood concentrations, either in a fasting state or after loading. Patients with an initial above-median increase in TG blood concentration after butter loading (>38%) before the beginning of the study, and who smoked cigarettes with a greater content of nicotine and tar, preferred vodka and had lower values of aminotransferases. CONCLUSION: Fasting and postprandial blood glucose, TC and TG concentrations had no relationship with the outcome of anti-relapse treatment. However, they presented some associations with the pathomechanism of addiction to nicotine.

The Polish Version of the Yale-Brown Obsessive-Compulsive Scale, Modified to Reflect Obsessions and Compulsions Related to Heavy Drinking (YBOCS-hd-PL).

BACKGROUND: The aim of the research work was to present the process of adapting the Polish version of the YBOCS-hd by Modell and colleagues (Alcohol Clin Exp Res 1992;16:266) to Polish conditions and to characterize the psychometric validation of the measure (e.g., validity, internal structure, and reliability). The scale is a self-assessment method consisting of 10 statements designed for measuring the severity of obsessive and compulsive craving-related thoughts and behaviors in alcohol-dependent or alcohol-abusing patients. METHODS: The study was carried out in a group of 550 patients diagnosed with alcohol dependence syndrome, 510 of whom (396 males and 114 females) were included in the final analysis. The patients were interviewed during the third week of therapy by the Polish version of the Yale-Brown Compulsive Scale Modified to Reflect Obsessions and Compulsions Related to Heavy Drinking (YBOCS-hd-PL), the Penn Alcohol Craving Scale (PACS), Short Alcohol Dependence Data Questionnaire (SADD), and the "compulsive" subscale of SCL-90. RESULTS: The YBOCS-hd-PL is characterized by good psychometric properties. Factor analysis identified 2 factors corresponding to the structure of the original version. Its internal consistency, assessed on the basis of Cronbach's alpha, is satisfactory: 0.84 for YBOCS-hd-PL (overall), 0.75 for factor 1 (obsessive thoughts), and 0.79 for factor 2 (compulsive behaviors). The discriminant power of the questions ranged from 0.46 to 0.68 (p < 0.001). For the adapted YBOCS-hd-PL, significant correlations were found between its scores and the PACS and the "compulsive" subscale of the SCL-90 scale. The obtained results indicate the Polish version of the YBOCS-hd (YBOCS-hd-PL) proved to be a reliable and valid instrument. CONCLUSIONS: In view of its very good psychometric properties, the Polish version of the YBOCS-hd can be recommended as an instrument for assessment of alcohol craving and its obsessive and compulsive aspects in individuals with alcohol use disorders.

Oxidoreductive homeostasis in alcohol-dependent male patients and the risk of alcohol drinking relapse in a 6-month follow-up.

Disturbances in the central signaling of reactive oxygen species (ROS) in response to energy intake are recognized as taking part in appetitive and consummative phases of eating disorders. This study aimed to verify the hypothesis that blood oxidoreductive balance can also affect demand for energy substances, such as alcoholic beverages in alcohol-dependent individuals, as well as the severity of their alcohol dependence and risk of drinking relapse. The following values were determined in the blood of 54 alcohol-dependent male patients after alcohol withdrawal, again after 4 weeks and after 6 months: the aldehyde products of lipid peroxidation (malonyl dialdehyde [MDA] and 4-hydroxynonenal [4-HNE]), nitric oxide (NO) metabolites, total antioxidant status (TAS), the blood activities of glutathione peroxidase (GSHpx), superoxide dismutase (SOD), glutathione reductase (GSHred), blood glucose, and lipids. Alcoholics who relapsed during 6 months of observation (n = 31, 57%) compared with patients who maintained alcohol abstinence for 6 months (n = 23, 43%) differed only in relation to initial and final NO metabolite serum concentrations. The risk of alcohol drinking relapse was lower in patients with an above-median initial blood concentration of NO metabolites and TAS. The oxidative stress parameters correlated with alcohol-dependence severity markers. No significant correlations between the studied antioxidant balance parameters and markers of nutritional status, including blood glucose and lipids, were found. Although the results of our study have some limitations and require further investigation, they suggest the role of oxidoreductive balance in the pathomechanisms of alcohol dependence and drinking relapse. In addition, due to a lack of association found between blood oxidative stress parameters and BMI, blood glucose, and lipid concentrations, they show the presence of disturbances in systemic ROS signaling in response to energy availability in alcoholics after alcohol withdrawal.

Evaluation of the Effectiveness of Preoperative Physiotherapy Using the Lysholm-Gillquist Scale in Patients Qualified for Surgical Arthroscopic Anterior Cruciate Ligament Reconstruction - Pilot Study.

BACKGROUND: Recent years have seen a noticeable increase in the number of people experiencing total damage to the anterior cruciate ligament in the knee joint. The causes are many, but increased sporting activity among people who generally lead a hypokinetic lifestyle is regarded as the most important factor. Researchers are seeking to optimize the surgical treatment and rehabilitation. AIM OF THE STUDY: To evaluate the effectiveness of preoperative physiotherapy according to the Lysholm and Gillquist scale in patients scheduled for arthroscopic anterior cruciate ligament reconstruction. MATERIAL AND METHODS: The study involved a random sample of 30 patients with confirmed complete rupture of anterior cruciate ligament (ACL) qualified for surgical ACL reconstruction. Within this group, an experimental group consisted of 15 patients (mean age 41.0 ± 7 years) who attended physiotherapy before surgery based on recognized therapeutic models. A control group consisted of 15 patients (mean age 39.0 ± 9 years). The Lysholm and Gillquist 100-point scale was used for assessment. Student's t test, the Mann-Whitney U test and the Wilcoxon test were used for statistical analysis. The level of statistical significance was set at p < 0.05. RESULTS: The operated knee improved functionally in both the experimental and control group. In the experimental group, the difference was 20 points and was statistically significant at p = 0.000. In the control group, the difference was 6 points, which was also within the limit of statistical significance at p = 0.002. CONCLUSIONS: 1. Patients with total ACL rupture attending a pre-operative rehabilitation program led by a physiotherapist (experimental group) achieved greater improvement in functional status compared with the control group. 2. These results indicate a need to analyze the impact ofpreoperative rehabilitation on the final outcome of patients after complete ACL rupture.

O2(X³Σg⁻) and O2(a¹Δg) charge exchange with simple ions.

We present theory and experiments which describe charge transfer from the X³Σg⁻ and a(1)Δg states of molecular oxygen and atomic and molecular cations. Included in this work are new experimental results for O2(a(1)Δg) and the cations O(+), CO(+), Ar(+), and N2⁺, and new theory based on complete active space self-consistent field method calculations and an extended Langevin model to calculate rate constants for ground and excited O2 reacting with the atomic ions Ar(+), Kr(+), Xe(+), Cl(+), and Br(+). The T-shaped orientation of the (X - O2)(+) potential surface is used for the calculations, including all the low lying states up to the second singlet state of the oxygen molecule b¹Σ(g)⁺. The calculated rate constants for both O2(X³Σg⁻) and O2(a(1)Δg) show consistent trends with the experimental results, with a significant dependence of rate constant on charge transfer exothermicity that does not depend strongly on the nature of the cation. The comparisons with theory show that partners with exothermicities of about 1 eV have stronger interactions with O2, leading to larger Langevin radii, and also that more of the electronic states are attractive rather than repulsive, leading to larger rate constants. Rate constants for charge transfer involving O2(a(1)Δg) are similar to those for O2(X³Σg⁻) for a given exothermicity ignoring the electronic excitation of the O2(a(1)Δg) state. This means (and the electronic structure calculations support) that the ground and excited states of O2 have about the same attractive interactions with ions.

Two-photon and time-resolved fluorescence spectroscopy as probes for structural determination in amyloid-ß peptides and aggregates.

The development of new sensitive methods for the detailed collection of conformational and morphological information about amyloids is crucial for the elucidation of critical questions regarding aggregation processes in neurodegenerative diseases. The combined approach of two-photon and time-resolved fluorescence spectroscopy described in this report interrogates the early conformational dynamics seen in soluble oligomers of amyloid-ß(1-42). Concentration-dependent aggregation studies using two-photon absorption show enhanced sensitivity toward conformational changes taking place in the secondary structure of the amyloid peptide as aggregation proceeds. Fluorescence lifetimes and changes in anisotropy values indicate Förster-type energy transfer occurring as a function of aggregation state. The sensitivity of our two-photon methodology is compared to that of circular dichroism (CD) spectroscopy, and the results indicate that the two-photon absorption cross-section method exhibits superior sensitivity. A theoretical model is developed that, together with electronic structure calculations, explains the change in cross section as a function of aggregation in terms of interacting transition dipoles for aggregates showing stacked or parallel structures. This suggests that the two-photon method provides a sensitive alternative to CD spectroscopy while avoiding many of the inherent challenges particular to CD data collection. The implication of this finding is significant, as it indicates that a two-photon-based technique used in conjunction with time-resolved fluorescence might be able to reveal answers to conformational questions about amyloid-ß(1-42) that are presently inaccessible with other techniques.

Modeling the electron-impact dissociation of methane.

The product yield of the electron-impact dissociation of methane has been studied with a combination of three theoretical methods: R-matrix theory to determine the electronically inelastic collisional excitation cross sections, high-level electronic structure methods to determine excited states energies and derivative couplings, and trajectory surface hopping (TSH) calculations to determine branching in the dissociation of the methane excited states to give CH(3), CH(2), and CH. The calculations involve the lowest 24 excited-state potential surfaces of methane, up to the ionization energy. According to the R-matrix calculations, electron impact preferentially produces triplet excited states, especially for electron kinetic energies close to the dissociation threshold. The potential surfaces of excited states are characterized by numerous avoided and real crossings such that the TSH calculations show rapid cascading down to the lowest excited singlet or triplet states, and then slower the dissociation of these lowest states. Product branching for electron-impact dissociation was therefore estimated by combining the electron-impact excitation cross sections with TSH product branching ratios that were obtained from the lowest singlet and triplet states, with the singlet dissociation giving a comparable formation of CH(2) and CH(3) while triplet dissociation gives CH(3) exclusively. The overall branching in electron-impact dissociation is dominated by CH(3) over CH(2). A small branching yield for CH is also predicted.

Discrete movements of foot epithelium during adhesive locomotion of a land snail.

During the adhesive locomotion of land snails a series of short dark transverse bands, called pedal or foot waves, is visible ifa moving snail's ventral surface is observed through a sheet of glass. Moreover, the mucus secreted from the pedal glands and some pedal epithelial cells forms a thin layer which acts as a glue augmenting adherence, while also acting as a lubricant under the moving parts of the snail's foot. The relationships between velocity and the frequency of pedal waves as well as changes in the volume of small air bubbles under foot waves were analyzed by means of digital recordings made through a glass sheet on which the snails were moving. On the ventral surface of a moving snail foot, the adhering parts of the foot constituted about 80% of the total area, while several moving parts only about 20%. The single moving region of the foot (the pedal wave) amounted to about 3% of snail length. The epithelium in the region of the pedal wave was arched above the substrate and was also more wrinkled than the stationary epithelium, which enabled the forward motion of each specific point of epithelium during the passage of a pedal wave above it. The actual area of epithelium engaged by a pedal wave was at least 30% greater than the area of the epithelium as recorded through a glass sheet. In the region of the pedal wave, the tiny subepithelial muscles acting on the epithelium move it up in the front part of the wave, and then down at the end of the wave, operating vertically in relation to the substrate. In the middle part of the wave, the epithelium only moves forward. In summary, during the adhesive locomotion of snails, the horizontal movement of the ventral surface epithelium proceeds as temporally separate phases of upward, forward and downward movement.

A Locality Analysis of the Divide-Expand-Consolidate Coupled Cluster Amplitude Equations.

We present a thorough locality analysis of the divide-expand-consolidate amplitude equations for second-order Møller-Plesset perturbation theory and the coupled cluster singles doubles (CCSD) model, which demonstrates that the amplitude equations are local when expressed in terms of a set of local occupied and local unoccupied Hartree-Fock orbitals, such as the least-change molecular basis. The locality analysis thus shows that a CC calculation on a large molecular system may be carried out in terms of CC calculations on small orbital fragments of the total molecular system, where the sizes of the orbital fragment spaces are determined in a black box manner to ensure that the CC correlation energy is calculated to a preset energy threshold. A practical implementation of the locality analysis is described, and numerical results are presented, which demonstrate that both the orbital fragment sizes and the relative energy error compared to a full CC calculation are independent of the molecular system size.

Linear scaling coupled cluster method with correlation energy based error control.

Coupled cluster calculations can be carried out for large molecular systems via a set of calculations that use small orbital fragments of the full molecular orbital space. The error in the correlation energy of the full molecular system is controlled by the precision in the small fragment calculations. The determination of the orbital spaces for the small orbital fragments is black box in the sense that it does not depend on any user-provided molecular fragmentation, rather orbital spaces are carefully selected and extended during the calculation to give fragment energies of a specified precision. The computational method scales linearly with the size of the molecular system and is massively parallel.

Maximum locality in occupied and virtual orbital spaces using a least-change strategy.

A new strategy is introduced for obtaining localized orthonormal Hartree-Fock (HF) orbitals where the underlying principle is to minimize the size of the transformation matrix from the atomic orbital basis to the HF optimized orbital basis. The new strategy gives both localized occupied and localized virtual orbital spaces. The locality of the occupied orbital space is similar to one obtained using standard localization schemes. For the virtual space, standard localization schemes fail to give local orbitals while the new strategy gives a virtual space which has a locality similar to the one of a Lowdin orthonormalization of the atomic orbital basis. Since Lowdin orthonormalization gives the most local orthonormal basis functions in the sense that they have the largest similarity with the local atomic basis functions, the new strategy thus allows the orthonormal basis to become optimized without introducing significant delocalization.

An efficient algorithm for solving nonlinear equations with a minimal number of trial vectors: applications to atomic-orbital based coupled-cluster theory.

The conjugate residual with optimal trial vectors (CROP) algorithm is developed. In this algorithm, the optimal trial vectors of the iterations are used as basis vectors in the iterative subspace. For linear equations and nonlinear equations with a small-to-medium nonlinearity, the iterative subspace may be truncated to a three-dimensional subspace with no or little loss of convergence rate, and the norm of the residual decreases in each iteration. The efficiency of the algorithm is demonstrated by solving the equations of coupled-cluster theory with single and double excitations in the atomic orbital basis. By performing calculations on H(2)O with various bond lengths, the algorithm is tested for varying degrees of nonlinearity. In general, the CROP algorithm with a three-dimensional subspace exhibits fast and stable convergence and outperforms the standard direct inversion in iterative subspace method.