Immunogenicity and Efficacy of a Novel Multi-Antigenic Peptide Vaccine Based on Cross-Reactivity between Feline and Human Immunodeficiency Viruses.

For the development of an effective HIV-1 vaccine, evolutionarily conserved epitopes between feline and human immunodeficiency viruses (FIV and HIV-1) were determined by analyzing overlapping peptides from retroviral genomes that induced both anti-FIV/HIV T cell-immunity in the peripheral blood mononuclear cells from the FIV-vaccinated cats and the HIV-infected humans. The conserved T-cell epitopes on p24 and reverse transcriptase were selected based on their robust FIV/HIV-specific CD8⁺ cytotoxic T lymphocyte (CTL), CD4⁺ CTL, and polyfunctional T-cell activities. Four such evolutionarily conserved epitopes were formulated into four multiple antigen peptides (MAPs), mixed with an adjuvant, to be tested as FIV vaccine in cats. The immunogenicity and protective efficacy were evaluated against a pathogenic FIV. More MAP/peptide-specific CD4⁺ than CD8⁺ T-cell responses were initially observed. By post-third vaccination, half of the MAP/peptide-specific CD8⁺ T-cell responses were higher or equivalent to those of CD4⁺ T-cell responses. Upon challenge, 15/19 (78.9%) vaccinated cats were protected, whereas 6/16 (37.5%) control cats remained uninfected, resulting in a protection rate of 66.3% preventable fraction (p = 0.0180). Thus, the selection method used to identify the protective FIV peptides should be useful in identifying protective HIV-1 peptides needed for a highly protective HIV-1 vaccine in humans.

Effects of staff training and electronic event monitoring on long-term adherence to lung-protective ventilation recommendations.

PURPOSE: To investigate long-term effects of staff training and electronic clinical decision support (CDS) on adherence to lung-protective ventilation recommendations. MATERIALS AND METHODS: In 2012, group instructions and workshops at two surgical intensive care units (ICUs) started, focusing on standardized protocols for mechanical ventilation and volutrauma prevention. Subsequently implemented CDS functions continuously monitor ventilation parameters, and from 2015 triggered graphical notifications when tidal volume (VT) violated individual thresholds. To estimate the effects of these educational and technical interventions, we retrospectively analyzed nine years of VT records from routine care. As outcome measures, we calculated relative frequencies of settings that conform to recommendations, case-specific mean excess VT, and total ICU survival. RESULTS: Assessing 571,478 VT records from 10,241 ICU cases indicated that adherence during pressure-controlled ventilation improved significantly after both interventions; the share of conforming VT records increased from 61.6% to 83.0% and then 86.0%. Despite increasing case severity, ICU survival remained nearly constant over time. CONCLUSIONS: Staff training effectively improves adherence to lung-protective ventilation strategies. The observed CDS effect seemed less pronounced, although it can easily be adapted to new recommendations. Both interventions, which futures studies could deploy in combination, promise to improve the precision of mechanical ventilation.

Racial and Ethnic Disparities in Health and Health Care: an Assessment and Analysis of the Awareness and Perceptions of Public Health Workers Implementing a Statewide Community Transformation Grant in Texas.

INTRODUCTION: Little is known about the awareness of public health professionals regarding racial and ethnic disparities in health in the United States of America (USA). Our study objective was to assess the awareness and perceptions of a group of public health workers in Texas regarding racial health disparities and their chief contributing causes. METHODS: We surveyed public health professionals working on a statewide grant in Texas, who were participants at health disparities' training workshops. Multivariable logistic regression was employed in examining the association between the participants' characteristics and their perceptions of the social determinants of health as principal causes of health disparities. RESULTS: There were 106 respondents, of whom 38 and 35 % worked in health departments and non-profit organizations, respectively. The racial/ethnic groups with the highest incidence of HIV/AIDS and hypertension were correctly identified by 63 and 50 % of respondents, respectively, but only 17, and 32 % were knowledgeable regarding diabetes and cancer, respectively. Seventy-one percent of respondents perceived that health disparities are driven by the major axes of the social determinants of health. Exposure to information about racial/ethnic health disparities within the prior year was associated with a higher odds of perceiving that social determinants of health were causes of health disparities (OR 9.62; 95 % CI 2.77, 33.41). CONCLUSION: Among public health workers, recent exposure to information regarding health disparities may be associated with their perceptions of health disparities. Further research is needed to investigate the impact of such exposure on their long-term perception of disparities, as well as the equity of services and programs they administer.

Ontology-based data integration between clinical and research systems.

Data from the electronic medical record comprise numerous structured but uncoded elements, which are not linked to standard terminologies. Reuse of such data for secondary research purposes has gained in importance recently. However, the identification of relevant data elements and the creation of database jobs for extraction, transformation and loading (ETL) are challenging: With current methods such as data warehousing, it is not feasible to efficiently maintain and reuse semantically complex data extraction and trans-formation routines. We present an ontology-supported approach to overcome this challenge by making use of abstraction: Instead of defining ETL procedures at the database level, we use ontologies to organize and describe the medical concepts of both the source system and the target system. Instead of using unique, specifically developed SQL statements or ETL jobs, we define declarative transformation rules within ontologies and illustrate how these constructs can then be used to automatically generate SQL code to perform the desired ETL procedures. This demonstrates how a suitable level of abstraction may not only aid the interpretation of clinical data, but can also foster the reutilization of methods for un-locking it.

Feline immunodeficiency virus (FIV) vaccine efficacy and FIV neutralizing antibodies.

A HIV-1 tier system has been developed to categorize the various subtype viruses based on their sensitivity to vaccine-induced neutralizing antibodies (NAbs): tier 1 with greatest sensitivity, tier 2 being moderately sensitive, and tier 3 being the least sensitive to NAbs (Mascola et al., J Virol 2005; 79:10103-7). Here, we define an FIV tier system using two related FIV dual-subtype (A+D) vaccines: the commercially available inactivated infected-cell vaccine (Fel-O-Vax(®) FIV) and its prototype vaccine solely composed of inactivated whole viruses. Both vaccines afforded combined protection rates of 100% against subtype-A tier-1 FIVPet, 89% against subtype-B tier-3 FIVFC1, 61% against recombinant subtype-A/B tier-2 FIVBang, 62% against recombinant subtype-F'/C tier-3 FIVNZ1, and 40% against subtype-A tier-2 FIVUK8 in short-duration (37-41 weeks) studies. In long-duration (76-80 weeks) studies, the commercial vaccine afforded a combined protection rate of at least 46% against the tier-2 and tier-3 viruses. Notably, protection rates observed here are far better than recently reported HIV-1 vaccine trials (Sanou et al., The Open AIDS J 2012; 6:246-60). Prototype vaccine protection against two tier-3 and one tier-2 viruses was more effective than commercial vaccine. Such protection did not correlate with the presence of vaccine-induced NAbs to challenge viruses. This is the first large-scale (228 laboratory cats) study characterizing short- and long-duration efficacies of dual-subtype FIV vaccines against heterologous subtype and recombinant viruses, as well as FIV tiers based on in vitro NAb analysis and in vivo passive-transfer studies. These studies demonstrate that not all vaccine protection is mediated by vaccine-induced NAbs.

Workflows in cancer treatment and their influence upon clinical documentation.

To establish single source cancer documentation for a complete comprehensive cancer center CCC we performed a systematic analysis of diagnostic, therapeutic and documentation workflows for 13 cancer entities. Results suggest that we will need three types of clinical documentation to cover all cancer entities of the Erlangen CCC. We expect to have a workflow for solid entities with inpatient treatment, one for solid entities treated ambulatory and one for non solid cancer entities.

Simvastatin ameliorates cauda equina compression injury in a rat model of lumbar spinal stenosis.

Lumbar spinal stenosis (LSS) is the leading cause of morbidity and mortality worldwide. LSS pathology is associated with secondary injury caused by inflammation, oxidative damage and cell death. Apart from laminectomy, pharmacological therapy targeting secondary injury is limited. Statins are FDA-approved cholesterol-lowering drug. They also show pleiotropic anti-inflammatory, antioxidant and neuroprotective effects. To investigate the therapeutic efficacy of simvastatin in restoring normal locomotor function after cauda equina compression (CEC) in a rat model of LSS, CEC injury was induced in rats by implanting silicone gels into the epidural spaces of L4 and L6. Experimental group was treated with simvastatin (5 mg/kg body weight), while the injured (vehicle) and sham operated (sham) groups received vehicle solution. Locomotor function in terms of latency on rotarod was measured for 49 days and the threshold of pain was determined for 14 days. Rats were sacrificed on day 3 and 14 and the spinal cord and cauda equina fibers were extracted and studied by histology, immunofluorescence, electron microscopy (EM) and TUNEL assay. Simvastatin aided locomotor functional recovery and enhanced the threshold of pain after the CEC. Cellular Infiltration and demyelination decreased in the spinal cord from the simvastatin group. EM revealed enhanced myelination of cauda equina in the simvastatin group. TUNEL assay showed significantly decreased number of apoptotic neurons in spinal cord from the simvastatin group compared to the vehicle group. Simvastatin hastens the locomotor functional recovery and reduces pain after CEC. These outcomes are mediated through the neuroprotective and anti-inflammatory properties of simvastatin. The data indicate that simvastatin may be a promising drug candidate for LSS treatment in humans.

Epidural abscess and cauda equina syndrome after percutaneous intradiscal therapy in degenerative lumbar disc disease.

BACKGROUND CONTEXT: Percutaneous intradiscal therapies are gaining popularity as a regenerative treatment option for spinal disc degeneration. The risks, benefits, and possible complications associated with such procedures have been poorly defined. As these procedures are performed with increasing frequency, the likelihood that clinicians will be faced with significant complications also increases. PURPOSE: The purpose of this study is to describe a significant complication of a percutaneous intradiscal bone marrow and adipose tissue transplantation for symptomatic lumbar disc degeneration. STUDY DESIGN: The study design is a case report. METHODS: Two weeks after an injection of adipose cells, bone marrow aspirate and plasma into his L3-L4 and L5-S1 lumbar discs, a 64-year-old patient presented to the emergency room with cauda equina syndrome, fever, and back pain. Magnetic resonance imaging diagnosed L3-L4 disc extrusion, discitis with osteomyelitis, and epidural abscess, resulting in emergency decompressive surgery. An epidural abscess was drained, extruded disc material was removed, and cultures obtained. Five days later, once afebrile on antibiotics, he underwent a definitive interbody arthrodesis and stabilization. RESULTS: Cauda equina syndrome resolved, osteomyelitis (methicillin-resistant Staphylococcus epidermidis) was treated, and instrumented arthrodesis stabilized the involved segment. CONCLUSIONS: Complications associated with the intradiscal injection of agents, such as stem cells, fibrin glue, adipose tissue, or bone marrow, have been poorly defined. Given the nature of the degenerating disc, serious adverse events, including discitis, osteomyelitis, and extrusion of disc contents, may occur.

S-Nitrosoglutathione administration ameliorates cauda equina compression injury in rats.

Lumbar spinal stenosis (LSS) causes ischemia, inflammation, demyelination and results in dysfunction of the cauda equina (CE), leading to pain and locomotor functional deficits. We investigated whether exogenous administration of S-nitrosoglutathione (GSNO), an endogenous redox modulating anti-neuroinflammatory agent, hastens functional recovery in a CE compression (CEC) rat model. CEC was induced in adult female rats by the surgical implantation of two silicone blocks within the epidural spaces of L4-L6 vertebrae. GSNO (50 µg/kg body weight) was administered by gavage 1 h after the injury, and the treatment was continued daily thereafter. GSNO induced change in the pain threshold was evaluated for four days after the compression. Tissue analyses and locomotor function evaluation were carried out at two weeks and four weeks after the CEC respectively. GSNO significantly improved motor function in CEC rats as evidenced by an increased latency on rotarod compared with vehicle-treated CEC rats. CEC induced hyperalgesia was decreased by GSNO. GSNO also increased the expression of VEGF, reduced cellular infiltration (H&E staining) and apoptotic cell death (TUNEL assay), and hampered demyelination (LFB staining and g-ratio). These data demonstrate that administration of GSNO after CEC decreased inflammation, hyperalgesia and cell death leading to improved locomotor function of CEC rats. The therapeutic potential of GSNO observed in the present study with CEC rats suggests that GSNO is a candidate drug to test in LSS patients.

Anterior lumbar interbody implants: importance of the interdevice distance.

Object. The implantation of interbody fusion cages allows for the restoration of disc height and the enlargement of the neuroforaminal space. The purpose of this study was to compare the extent of subsidence occurring after conventional cage placement compared to a novel wider cage placement technique. Methods. This study is a retrospective evaluation of radiographs of patients who underwent stand-alone single level anterior lumbar interbody fusion with lordotic titanium cages and rhBMP-2. Fifty-three patients were evaluated: 39 patients had wide cage placement (6 mm interdevice distance) and 14 had narrow cage placement (2 mm interdevice distance). Anterior and posterior intervertebral disc space heights were measured post-operatively and at follow-up imaging. Results. The decrease in anterior intervertebral disc space height was 2.05 mm versus 3.92 mm (P < .005) and 1.08 mm versus 3.06 mm in posterior disc space height for the wide cage placement and the narrow cage placement respectively. The proportion of patients with subsidence greater than 2 mm was 41.0% in the wide cage patients and 85.7% for the narrow cage patients (P < .005). Conclusions. The wider cage placement significantly reduced the amount of subsidence while allowing for a greater exposed surface area for interbody fusion.

IT infrastructure components to support clinical care and translational research projects in a comprehensive cancer center.

This paper presents the concept of an integrated IT infrastructure framework established at the comprehensive cancer center at the University Hospital Erlangen. The framework is based on the single source concept where data from the electronic medical record are reused for clinical and translational research projects. The applicability of the approach is illustrated by two case studies from colon cancer and prostate cancer research projects.

Community-based participatory approach to reduce breast cancer disparities in south Dallas.

BACKGROUND: South Dallas experiences significant disparities in breast cancer mortality, with a high proportion of stage III and IV diagnoses. To address these rates, the Dallas Cancer Disparities Community Research Coalition created an educational intervention to promote breast health and early detection efforts. OBJECTIVES: The goals of the intervention were to increase (a) knowledge regarding the chief contributing factors for breast cancer, (b) awareness of the importance of screening for early detection, and (c) the proportion of women who have engaged in appropriate breast cancer screening practices. METHODS: Eligibility criteria for this nonrandomized, controlled trial included women age 40 and older, English-speaking, and having no personal history of cancer. Control participants received written breast health educational materials. Intervention participants attended 8 weekly sessions that included interactive educational materials, cooking demonstrations, and discussions emphasizing primary and secondary breast cancer prevention. All study participants completed a 1-hour survey at baseline and 4 months later. RESULTS: There were 59 women were enrolled in the intervention and 60 in the control group. At follow-up, after controlling for baseline mammography status, women in the intervention group were 10.4 times more likely (95% confidence interval [CI], 2.9-36.4) to have received a screening mammogram in the last year compared with the control group. Intervention participants demonstrated statistically significantly higher rates of breast self-examination (odds ratio [OR], 3.0; 95% CI, 1.0-8.6) and breast cancer knowledge (p=.003). CONCLUSION: Lessons learned from this community-based participatory research (CBPR) study can be used to create sustainable cancer disparity reduction models that can be replicated in similar communities.

Using a prostate exam simulator to decipher palpation techniques that facilitate the detection of abnormalities near clinical limits.

INTRODUCTION: Prostate carcinoma (and other prostate irregularities and abnormalities) is detected in part via the digital rectal examination. Training clinicians to use particular palpation techniques may be one way to improve the rates of detection. METHODS: In an experiment of 34 participants with clinical backgrounds, we used a custom-built simulator to determine whether certain finger palpation techniques improved one's ability to detect abnormalities smaller in size and dispersed as multiples over a volume. The intent was to test abnormality cases of clinical relevance near the limits of size perceptibility (ie, 5-mm diameter). The simulator can present abnormalities in various configurations and record finger movement. To characterize finger movement, four palpation techniques were quantitatively defined (global finger movement, local finger movement, average intentional finger pressure, and dominant intentional finger frequency) to represent the qualitative definitions of other researchers. RESULTS: Participants who used more thorough patterns of global finger movement (V and L) ensured that the entire prostate was searched and detected more abnormalities. A higher magnitude of finger pressure was associated with the detection of smaller abnormalities. The local finger movement of firm pressure with varying intensities was most indicative of success and was required to identify the smallest (5-mm diameter) abnormality. When participants used firm pressure with varying intensities, their dominant intentional finger frequency was about 6 Hz. CONCLUSIONS: The use of certain palpation techniques does enable the detection of smaller and more numerous abnormalities, and we seek to abstract these techniques into a systematic protocol for use in the clinic.

Simvastatin protects bladder and renal functions following spinal cord injury in rats.

BACKGROUND: Urinary bladder and renal dysfunction are secondary events associated with spinal cord injury (SCI) in humans. These secondary events not only compromise quality of life but also delay overall recovery from SCI pathophysiology. Furthermore, in experimental models the effects of SCI therapy on bladder and renal functions are generally not evaluated. In this study, we tested whether simvastatin improves bladder and renal functions in a rat model of experimental SCI. METHODS: SCI was induced by controlled contusion of T9-T10 in adult female rats. Simvastatin (5 mg/Kg body weight) was administered at two hours after SCI and repeated every 24 hours until the end point. Simvastatin-treated SCI animals (simvastatin group) were compared with vehicle-treated SCI animals (vehicle group) in terms of the Basso Beattie Bresnahan score, tissue morphology, cell death, and bladder/renal functions. RESULTS: The urinary bladder of vehicle animals showed a 4.3-fold increase in size and a 9-fold increase in wet weight compared to sham animals. Following SCI, the urine to plasma osmolality ratio increased initially but decreased 1 week after SCI. Hematoxylin and eosin staining of bladder tissue showed transitional epithelial hyperplasia, degeneration of lamina propria, and enlargement of tunica adventia in addition to detrusor muscle hypertrophy. Rats treated with simvastatin for 14 days displayed remarkable recovery by showing decreased bladder size and maintenance of a normal urine/plasma osmolality ratio, in addition to improved locomotion. The muscularis layer of the bladder also regained its compact nature in simvastatin animals. Moreover, SCI-induced renal caspase-3 activity was significantly decreased in the simvastatin group indicating the ability of simvastatin to reduce the renal tubular apoptosis. CONCLUSION: Post-injury administration of simvastatin ameliorates bladder and renal dysfunction associated with SCI in rats.

Quantifying palpation techniques in relation to performance in a clinical prostate exam.

This paper seeks to quantify finger palpation techniques in the prostate clinical exam, determine their relationship with performance in detecting abnormalities, and differentiate the tendencies of nurse practitioner students and resident physicians. One issue with the digital rectal examination (DRE) is that performance in detecting abnormalities varies greatly and agreement between examiners is low. The utilization of particular palpation techniques may be one way to improve clinician ability. Based on past qualitative instruction, this paper algorithmically defines a set of palpation techniques for the DRE, i.e., global finger movement (GFM), local finger movement (LFM), and average intentional finger pressure, and utilizes a custom-built simulator to analyze finger movements in an experiment with two groups: 18 nurse practitioner students and 16 resident physicians. Although technique utilization varied, some elements clearly impacted performance. For example, those utilizing the LFM of vibration were significantly better at detecting abnormalities. Also, the V GFM led to greater success, but finger pressure played a lesser role. Interestingly, while the residents were clearly the superior performers, their techniques differed only subtly from the students. In summary, the quantified palpation techniques appear to account for examination ability at some level, but not entirely for differences between groups.

Assessment of spine surgery outcomes: inconsistency of change amongst outcome measurements.

BACKGROUND CONTEXT: Outcomes of spinal treatments are evaluated by clinical relevance: the proportion of patients who reach a minimum clinically important outcome change. Outcomes are evaluated through multiple measurements, and the inconsistency of outcome change across measurements is not known. PURPOSE: The primary purpose of this study was to illustrate outcome inconsistencies after spinal surgery. Secondary goals of this study were to develop an index of overall change that incorporates outcome inconsistencies, to relate the index of overall change to patients' global assessment and satisfaction with treatment, to relate the index of global change to an intuitively understandable outcome: the level of tolerable pain. STUDY DESIGN: This study is a review of prospectively collected patient-reported outcomes data. PATIENT SAMPLE: Four hundred sixty patients from a large multicenter database were chosen. Those patients were included in the sample because they had undergone lumbar surgery and had baseline and 1-year follow-up scores. Baseline and 1-year follow-up scores for Oswestry Disability Index (ODI), physical component summary (PCS) of the Medical Outcome Study Short Form-36 (SF-36), numerical back and leg pain scales, and 1-year scores for satisfaction with results were included in the study. OUTCOME MEASURES: The outcome measures of the study were preoperative and 1-year postoperative scores for ODI, PCS, back pain scale, leg pain scale, health transition item of the SF-36, and satisfaction with results scales. METHODS: Oswestry Disability Index, SF-36, and pain scales were administered before and 1 year after spinal surgery. Satisfaction with results questionnaires were administered 1 year after surgery. The following threshold values were previously established and were used to evaluate outcome changes: minimum clinically important difference (MCID), substantial clinical benefit (SCB), and standard error of the mean. The following proportions of patients were determined according to outcome changes: "deteriorated," "no change," "below MCID," "above MCID," and "above SCB." The consistency of outcome change was determined amongst the four outcome measures. An index of overall change was developed and related to patients' answers to the health transition item of the SF-36 and to the satisfaction with results scale. The overall change index was also compared with the tolerable pain level. RESULTS: Only 40.5% of patients report consistent outcome changes on all four measures. The overall change index was significantly correlated to the global change and satisfaction scale (rho=.67, p less than .001). The overall change index was clearly associated with the tolerable pain level. CONCLUSIONS: Efforts should be made to take into account the inconsistency of outcomes and to make clinical relevance more readily understandable by patients and clinicians.

An unusual occurrence of chondromyxoid fibroma with secondary aneurysmal bone cyst in the cervical spine.

BACKGROUND CONTEXT: Chondromyxoid fibroma (CMF) and aneurysmal bone cysts (ABCs) are rare bone tumors and even rarer in the spine. To date, no report has been made of CMF with secondary ABC in the cervical spine. PURPOSE: The purpose of this study was to describe the diagnosis and surgical treatment of a case of CMF with secondary ABC of C6, a rare occurrence in an uncommon location. STUDY DESIGN: The study design is a case report. METHODS: A 27-year-old woman presented with numbness with paresthesias of the right upper extremity. Diagnostic imaging revealed diffuse enlargement of the right C6 lamina extending into the pedicle and medial facet joint. Surgical treatment consisted of complete C6 laminectomy, total resection of the extradural cervical mass, posterior lateral fusion at C5-C7, and posterior segmental instrumentation from C5 to C7. Histopathology was consistent with CMF with secondary ABC. RESULTS: Laminectomy and instrumented segmental fusion provided an excellent clinical outcome. The instrumented fusion maintained the sagittal balance of the spine and stabilized across a complete facetectomy. The excision will likely avoid recurrence of the lesion. CONCLUSIONS: Treatment of CMF and ABC is challenging in the spine because of the proximity to neural structures. Aggressive surgical treatment makes recurrence less likely but creates the risk of spinal instability. Adequate surgical treatment needs to provide spinal stability.

Interpreter services in emergency medicine.

Emergency physicians are routinely confronted with problems associated with language barriers. It is important for emergency health care providers and the health system to strive for cultural competency when communicating with members of an increasingly diverse society. Possible solutions that can be implemented include appropriate staffing, use of new technology, and efforts to develop new kinds of ties to the community served. Linguistically specific solutions include professional interpretation, telephone interpretation, the use of multilingual staff members, the use of ad hoc interpreters, and, more recently, the use of mobile computer technology at the bedside. Each of these methods carries a specific set of advantages and disadvantages. Although professionally trained medical interpreters offer improved communication, improved patient satisfaction, and overall cost savings, they are often underutilized due to their perceived inefficiency and the inconclusive results of their effect on patient care outcomes. Ultimately, the best solution for each emergency department will vary depending on the population served and available resources. Access to the multiple interpretation options outlined above and solid support and commitment from hospital institutions are necessary to provide proper and culturally competent care for patients. Appropriate communications inclusive of interpreter services are essential for culturally and linguistically competent provider/health systems and overall improved patient care and satisfaction.

Advances in FIV vaccine technology.

Advances in vaccine technology are occurring in the molecular techniques used to develop vaccines and in the assessment of vaccine efficacy, allowing more complete characterization of vaccine-induced immunity correlating to protection. FIV vaccine development has closely mirrored and occasionally surpassed the development of HIV-1 vaccine, leading to first licensed technology. This review will discuss technological advances in vaccine designs, challenge infection assessment, and characterization of vaccine immunity in the context of the protection detected with prototype and commercial dual-subtype FIV vaccines and in relation to HIV-1.

Studies of the thermodynamic properties of hydrogen gas in bulk water.

The thermodynamic properties of hydrogen gas in liquid water are investigated using Monte Carlo molecular simulation and the quasichemical theory of liquids. The free energy of hydrogen hydration obtained by Monte Carlo simulations agrees well with the experimental result, indicating that the classical force fields used in this work provide an adequate description of intermolecular interactions in the aqueous hydrogen system. Two estimates of the hydration free energy for hydrogen made within the framework of the quasichemical theory also agree reasonably well with experiment provided local anharmonic motions and distant interactions with explicit solvent are treated. Both quasichemical estimates indicate that the hydration free energy results from a balance between chemical association and molecular packing. Additionally, the results suggest that the molecular packing term is almost equally driven by unfavorable enthalpic and entropic components.